• Yes, if patient/client displays signs/symptoms of active allergic reaction that may affect the appropriateness or safety of procedures, including potential exacerbation by procedures. 

Is medical consult advised?  

• Yes, if patient/client presents with signs/symptoms of a potential allergic etiology (e.g., urticaria and/or angioedema) for which diagnosis has not been  previously made by a physician or nurse practitioner.
• Yes, if patient/client presents with signs/symptoms of known allergic etiology (e.g., urticaria and/or angioedema) for which management/treatment has not been optimized.

• Yes, if patient/client displays signs/symptoms of active allergic reaction that may affect the appropriateness or safety of procedures, including potential exacerbation by procedures.
  

Is medical consult advised? 

• See above.
• Yes, if after history-taking, questions remain about potential exposure to allergens in the dental/dental hygiene office setting (particularly if mitigation is difficult).
• Yes, if, after history-taking, questions remain about the cause of previous reaction to local anaesthetics (when such anaesthetics are likely to be used during the visit)¹.

Is medical clearance required? 

• Yes, if asthma is suspected to be severe and unstable.
• Yes, if there is a history of hereditary angioedema² (for assessment and potential use of preventive agents).

Is antibiotic prophylaxis required?  

• No, not typically (although prolonged use and/or high doses of systemic corticosteroids may warrant consideration of antibiotic prophylaxis in light of potential immunosuppression)³.

Is postponing treatment advised?

• Yes, if there is acute respiratory distress. If anaphylaxis⁴ or angioedema of the tongue, pharyngeal tissues or larynx is suspected, emergency protocol should be initiated, and prompt transfer to an emergency department is indicated. Immediate intervention (e.g., administration of epinephrine) is required for these life-threatening conditions. 
• Yes, if patient/client is currently manifesting signs/symptoms of allergy that may impede safety of dental hygiene procedures.
• Yes, if there is suspicion of current or potential allergic reaction to dental/dental hygiene materials.
• Yes, for dental procedures requiring local anaesthesia when the patient/client’s past history reveals confirmed allergy, or suspicion of allergy, to local anaesthetic. Dental/dental hygiene procedures that do not require anaesthesia may be performed in the interim.

• When a patient/client reports an allergy to a product or drug likely to be used in a dental/dental hygiene appointment, the chart should be clearly marked to draw attention to the allergy.
• A history of allergy to metals⁵ must be followed up, because: 1/ metal instruments are routinely used in a patient/client’s mouth; and 2/ amalgam restorative material contains metal.
• Nonlatex products must be available when treating a patient/client with a latex allergy. Dental products that may contain latex include: gloves, latex barriers, and elastic on face mask; rubber dam; rubber polishing cup; dental unit hoses; rubber on local anaesthetic cartridge; and rubber tubing on stethoscope and blood pressure cuff. Barriers should be applied with products that are only available in latex.
• Noniodine products must be available when treating a patient/client with an iodine allergy. Dental/related products that may contain iodine include: antiseptic solutions for use in the oral cavity; anti-infective hand soaps; and surface disinfectant solutions.⁶
• If the patient/client is experiencing postnasal discharge (e.g., from allergic rhinitis), the semisupine chair position should be used. The supine position may result in choking or coughing.
• The patient/client with a known food allergy should carry an auto-injector of epinephrine to facilitate appropriate emergency treatment at the earliest sign of a reaction. The wearing of a MedicAlert identifier should also be encouraged.  
• Two forms of allergy are particularly relevant for the dental hygienist. A type I, or anaphylactic (immediate), reaction, may present in the dental/dental hygiene office with an acutely life-threatening situation. A type IV, or delayed, reaction is seen clinically as contact dermatitis⁷, which affects a significant number of oral health professionals.
• Acute allergic reaction is one of the most common medical emergencies in the dental/dental hygiene office. Of particular importance is patient/client-reported allergy to a local anaesthetic, analgesic, or antibiotic. Such a history must be expanded to determine what the specific drug was and how the patient/client reacted to it. Signs and symptoms suggestive of a true allergic reaction include urticaria, swelling, rash, dyspnea, chest tightness, rhinorrhea (clear nasal discharge), and conjunctivitis. Often, a patient/client may mislabel a non-allergic reaction as an “allergy”, such as syncope after injection of a local anaesthetic, nausea or vomiting after ingestion of codeine, or gastrointestinal discomfort or diarrhea after taking an antibiotic. 
• Pre-anaesthetic assessment is key in preventing allergic reactions in the dental/dental hygiene office. The patient/client with multiple allergies (e.g., asthma, hay fever, and food allergy) is at elevated risk for allergic reactions to medications, including local anaesthetic agents. While only 1% or so of all reactions that occur during local anaesthetic administration are true allergic reactions, a documented local anaesthetic allergy represents an absolute contraindication to use⁸. Allergic response spans the spectrum from dermatitis and bronchospasm to life-threatening reaction.
• Antibiotics such as penicillins and sulfonamides are frequently associated with allergic responses, whereas others such as erythromycin are rarely implicated.
• Non-steroidal anti-inflammatory drugs (NSAIDs) can be problematic for persons with asthma. 1% to 5% of patients/clients with asthma are unable to take non-selective NSAIDs (e.g., ibuprofen, naproxen, and diclofenac, as well as aspirin) without developing a severe and sometimes life-threatening asthma attack. Therefore, NSAIDs should be used cautiously, if at all, in patients/clients with asthma; history of NSAID allergy is an absolute contraindication to use.
• The dental/dental hygiene management of asthma is primarily focused on preventing severe asthma attacks from happening in the office and dealing with an attack if it occurs.
• Mouth rinses and toothpastes containing antiseptics, astringents, phenolic compounds, and/or flavouring agents can cause hypersensitivity reactions affecting the oral mucosa or lips.
• Allergic reactions to various dental cartridge contents can occur. In particular, allergy to sulfites (acetone sodium bisulfite and sodium metabisulfite), which are antioxidants used as preservatives for the vasoconstrictor in local anaesthetic solutions), has been reported. Patients/clients with asthma may be particularly susceptible. Therefore, local anaesthetics without vasoconstrictor (and therefore without sodium bisulfite or metabisulfite) must be used when there is a history of sulfite sensitivity⁹.
• If respiratory distress is suspected secondary to an allergic reaction, the following should occur: terminate procedures; place patient/client in the semi-erect position; provide basic life support as required; summon medical assistance; administer epinephrine; monitor vital signs; maintain airway; administer additional drugs (e.g., antihistamine, corticosteroid); administer oxygen; and transfer patient/client to hospital.
• Angioedema involving the larynx and/or pharynx can cause asphyxiation — immediate treatment with epinephrine is necessary. Hereditary angioedema can be provoked by dental surgery and trauma, and it is best managed by preventive measures¹⁰, because this form of angioedema does not respond well to epinephrine or antihistamines.
• Patients/clients exhibiting oral contact stomatitis or plasma cell gingivitis should be counseled to cease use of toothpastes and chewing gum containing cinnamon flavouring agents. If improvement is not rapid, careful dietary history may be required to identify an allergenic source. In cases of severe symptomatology, topical steroid application in the form of mouthwash, gel, or ointment may accelerate healing. 
• Azo and nonazo dyes used in toothpaste have been reported to cause anaphylactic-like reactions.
• In the atopic (i.e., allergy-prone) patient/client, the use of topical fluoride can induce an allergic reaction. However, this is a rare occurrence.
• Contact dermatitis¹¹, particularly affecting the hands, can occur secondary to materials (e.g., acrylates) encountered in the dental/dental hygiene setting. While routine use of gloves has decreased work-place incidence, latex gloves and glove powder are allergens for some persons. As well, some hand soaps used by oral healthcare professionals can result in allergic reactions.

• Oral and perioral lesions can be produced by type I hypersensitivity reactions to various foods, drugs, or anaesthetic agents, usually manifesting as urticaria or angioedema (described further below under “Related signs and symptoms”). The reaction is usually rapid, with the lesion developing within a short time after coming into contact with the antigen. The painless, soft tissue swelling may cause burning or itching. Lip swelling is a particularly common manifestation of angioedema. Spontaneous resolution usually occurs in 1 to 3 days; resolution and symptom relief are aided by the use of oral antihistamines (e.g., diphenhydramine). Reaction involving the tongue, pharynx, or larynx with respiratory distress requires epinephrine intramuscularly or subcutaneously, in addition to oxygen, as well as antihistamines once the immediate danger is over.
• Cyanosis of the mucous membranes can be a manifestation of an immediate anaphylactic reaction. 
• Oral lesions resulting from type III (immune complex) hypersensitivity reactions to foods, drugs, or other agents placed within the mouth can manifest as white, red, or ulcerative¹² lesions. These lesions usually manifest within 24 hours of antigen contact.
• Delayed type allergic reactions can manifest as angioedema of the lips, tongue, and pharynx.   
• Erythema multiforme — an immune complex reaction that appears as a polymorphous eruption of classic “target” lesions, macules, and erosions — can occur on the oral mucosa (as well as skin) as a result of certain drug allergies (e.g., sulfa antibiotics, as well as sulfonylurea hypoglycemic agents used in the treatment of type 2 diabetes).
• Allergic contact mucositis can occur as a result of delayed hypersensitivity (type IV) to topically applied substances at home (e.g., lipsticks and face powder) or in the dental/dental hygiene setting (e.g., preservatives in local anaesthetics, components of topical medications¹³, mouthwashes, iodine, acrylates [such as methacrylates in composite resins and denture base materials], metal-based alloys [including mercury-containing dental amalgam, nickel, chromium, palladium, and cobalt], and flavouring agents in toothpaste and chewing gum)¹⁴. The mucosa becomes red and edematous, often accompanied by pruritis and a burning sensation. The mucositis occurs where the allergen has contacted the mucosa, giving it a shiny, smooth appearance with firmness to palpation. Small vesicles and ulcers may also occur in the affected areas for a stomatitis appearance.
• Allergic contact stomatitis (a type IV hypersensitivity reaction) is most commonly associated with the consumption of products containing cinnamon derivatives, including cinnaldehyde and cinnamon essential oil; other known triggers are carvone¹⁵, menthol essential oil, and spearmint oil¹⁶. Stomatitis lesions typically appear at mucosal sites that are in direct contact with the causal agent. Lesions usually white or even lichenoid, although red and ulcerative lesions may be seen, as may vesicles. Edema and a burning sensation are often present. Because of the cascade of cellular events involved, contact stomatitis does not become evident for several hours or even days after exposure to the antigen¹⁷.
• “Denture sore mouth” refers to inflammatory changes of mucous membranes developing beneath dentures. It can be caused by allergy to acrylic resins used to make dentures. The palatal oral mucosa and maxillary ridges are most frequently involved, with tissue appearing bright red and edematous. The patient/client complains of soreness, rawness, dryness, and burning.  
• Plasma cell gingivitis is a form of contact allergy to cinnamon-containing substances found in toothpaste and chewing gum. This condition predominately affects the attached gingiva, manifesting as a fiery red bilateral band, often edematous appearing but without ulceration. As well, the tongue may be atrophic and red, and the commissures may be reddened, cracked, and fissured (angular cheilitis). It is much less common now than in the 1970s, which may be due to nonallergenic changes made to chewing gum formulas and ingredients.
• Allergic reactions to drugs taken systemically or used topically may affect the oral mucous membranes. Clinical appearance varies from red, erythematous lesions to urticaria to vesiculo-ulcerative eruption. In less intense reactions, the mucosa exhibits diffuse redness. When the tongue is affected, the pattern may be similar to the changes of vitamin B12 deficiency and anemia (i.e., smooth, red appearance with pain and burning).
• Lichenoid drug eruptions in the oral cavity (and on the skin), similar to the lesions of lichen planus, can be seen after taking certain drugs (e.g., levamisole, quinidine, thiazide diuretics, gold, methyldopa, phenothiazines, and some antibiotics). Lichenoid mucosal lesions are also occasionally associated with dental amalgam restoration materials such as mercury.
• Fixed drug eruptions can occur on the lips and, less commonly, the mucous membranes of the oral cavity¹⁸. There may be single or multiple clusters of macules or multiple slightly raised reddish patches. After sudden appearance following a latent period of several days after drug introduction, the lesions subside when the causative drug is discontinued. Pruritus and pain may be associated with the lesions. 

• An allergy is a hypersensitivity reaction that is acquired through exposure to a specific substance (i.e., allergen) that normally is considered harmless; re-exposure to the allergen increases the likelihood of reaction¹⁹. Clinical manifestations range from mild, delayed reactions developing as long as 48 hours after exposure to the antigen to immediate and life-threatening reactions (anaphylaxis type) occurring with seconds of exposure. Generally, the more rapid the onset of signs/symptoms after exposure to the allergen, the more severe the ultimate reaction.
• Between 15% to 25% of North Americans have an allergy to some substance, including about 4.5% who have asthma, 4% who are allergic to insect stings, and 5% who are allergic to one or more drugs. Food allergies²⁰ affect 5% to 6% of young children and 3% to 4% of adults in Western countries.
• An allergic reaction may manifest solely in the skin or respiratory tract, or it may accompany or follow other systemic responses. In slowly evolving generalized allergic reactions, respiratory distress usually follows skin and gastrointestinal reactions and precedes cardiovascular manifestations.
• Urticaria (hives) is a vascular reaction of the skin characterized by the transient appearance of smooth, well demarcated, slightly elevated plaques (wheals) or papules that are red and often accompanied by severe pruritus. The lesions blanche with the application of pressure, and they often have advancing and receding edges. Most urticaria is self-limited and of short duration (and fades without scarring, with hyper- and hypopigmentation being very unusual), rarely lasting more than several days²¹. However, it may be recurrent over weeks²². Urticaria (acute, chronic, or both) affects between 15% and 25% of the people at some time in their lives, most commonly occurring in children and young adults. Of those patients/clients affected, 50% have both urticaria and angioedema, 40% have urticaria alone, and 10% have angioedema only. Acute urticaria does not cause mortality unless it is associated with angioedema involving the upper airways. Morbidity depends on the duration and severity of the urticaria.
• Angioedema is a subcutaneous extension of urticaria, which manifests as diffuse, nonpitting edema below the dermis (in contrast to urticaria’s transient extravasation of plasma into the dermis in more circumscribed form)²³ or below the mucous membranes (including the upper respiratory and gastrointestinal tracts). The skin covering the swelling appears normal, and there is usually no pruritis. Angioedema typically causes localized swelling of the periorbital area, extremities, larynx, and/or oral and pharyngeal structures. Triggering agents include certain foods or drugs, insect stings or bites, cold, heat, and latex²⁴.
• Generalized anaphylaxis (“anaphylactic shock”) is the most life-threatening allergic reaction. It usually develops quickly and reaches maximum intensity within 5 to 30 minutes of allergen exposure.
• Signs/symptoms of immediate anaphylaxis include:
  • skin and related manifestations (e.g., urticaria, pruritis, angioedema, flushing, feeling of hair standing on end, conjunctivitis, vasomotor rhinitis, and perspiration);
  • respiratory and related manifestations (e.g., cough, bronchospasm, wheezing, dyspnea, substernal tightness, chest pain, cyanosis of mucous membranes and nail beds, and laryngeal edema²⁵);
  • cardiovascular and related manifestations (e.g., pallor, light-headedness, anxiety, tachycardia, palpitations, hypotension, cardiac dysrhythmias, unconsciousness, and cardiac arrest); and
  • gastrointestinal manifestations (e.g., nausea, vomiting, abdominal cramps, and diarrhea).
• Fortunately, the most common allergic reactions associated with using allergenic products in the dental/dental hygiene setting are less dangerous than generalized anaphylaxis. These reactions (usually delayed hypersensitivity type) are typically characterized by: vesicles that break to form small ulcers; development of erythema, rash, and/or itching; and stinging and tissue sloughing²⁶.
• Drugs can be allergens, and patients/clients with multiple allergies are more likely to have allergic reactions to medications. Persons with autoimmune diseases (e.g., systemic lupus erythematosus) are at elevated risk of adverse drug reactions.
• While 5% to 10% of persons who are given the antibiotic penicillin develop an allergic reaction, systemic anaphylactic reaction is much rarer — about 1 in 10,000 patients/clients. Cross-reactivity with cephalosporins exists in 5% to 10% of penicillin-allergic patients/clients.
• In addition to Type 1 (anaphylactic type) hypersensitivity, drugs can also cause Type III (immune complex type or “serum sickness”) hypersensitivity²⁷ (again, penicillin being most commonly implicated) or Type IV (T-cell mediated or delayed) hypersensitivity²⁸.  
• Contact dermatitis (e.g., of the hands caused by latex gloves) often starts with reddening of the skin accompanied by swelling and vesicles. Eventually the affected area may become white, crusted, and scaly.
• The most common form of asthma — i.e., extrinsic asthma — is provoked by exposure to environmental allergens.
• Food/digestive allergies, skin allergies (e.g., eczema), and respiratory allergies (e.g., allergic rhinitis [hay fever]) are the most common allergies among children. While the prevalence of skin allergies decreases with age, the prevalence of respiratory allergies increases.

• Syed M, Chopra R, Sachdev V. Allergic Reactions to Dental Materials-A Systematic Review. J Clin Diagn Res. 2015 Oct;9(10):ZE04-9. doi: 10.7860/JCDR/2015/15640.6589. Epub 2015 Oct 1. PMID: 26557634; PMCID: PMC4625353. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4625353/  
• Becker DE. Drug allergies and implications for dental practice. Anesth Prog. 2013 Winter;60(4):188-97. doi: 10.2344/0003-3006-60.4.188. PMID: 24423421; PMCID: PMC3891459.
  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3891459/ 
• Wray D, Rees SR, Gibson J, Forsyth A. The role of allergy in oral mucosal diseases. QJM. 2000; 93(8):507-11.
  https://www.ncbi.nlm.nih.gov/pubmed/10924532
• Kaplan AP. Angioedema. World Allergy Organ J. 2008; 1(6):103-113.
  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3651192/
• Incorvaia C, Frati F, Sensi L, Riario-Sforza GG, Marcuccio F. Allergic inflammation and the oral mucosa. Recent Pat Inflamm Allergy Drug Discov. 2007; 1(1):35-8.
  https://www.ncbi.nlm.nih.gov/pubmed/19075964
• Tremblay S, Avon SL. Contact Allergy to Cinnamon: Case Report. JCDA. 2008; 74(5):445-448.
  https://www.cda-adc.ca/jcda/vol-74/issue-5/445.pdf
• Health Canada
  https://www.canada.ca/en/health-canada/services/healthy-living/your-health/food-nutrition/food-allergies.html
  https://www.canada.ca/en/health-canada/services/food-nutrition/food-safety/food-allergies-intolerances.html
• DermNet NZ
  https://www.dermnetnz.org/topics/fixed-drug-eruption/
• National Institute for Health and Care Excellence
  https://www.nice.org.uk/guidance/cg183 (Drug allergy: diagnosis and management)
• U.S. Centers for Disease Control and Prevention
  https://www.cdc.gov/nchs/data/databriefs/db121.pdf (Trends in Allergic Conditions Among Children: United States, 1997-2011)
• Medscape
  https://emedicine.medscape.com/article/137362-overview#showall (Urticaria)
  https://emedicine.medscape.com/article/756261-overview (Angioedema) 
• WebMD
  https://www.webmd.com/skin-problems-and-treatments/hereditary-angioedema#1 
• Pickett FA and Gurenlian JR. Preventing Medical Emergencies: Use of the Medical History in Dental Practice (3^rd edition). Baltimore/Philadelphia: Wolters Kluwer Health; 2015.
• Bowen DM (ed.) and Pieren JA (ed.). Darby and Walsh Dental Hygiene: Theory and Practice (5^th edition). St. Louis: Elsevier; 2020.
• Ibsen OAC and Peters SM. Oral Pathology For The Dental Hygienist (8^th edition). St. Louis: Elsevier; 2023.
• Regezi JA, Sciubba JJ, and Jordan RCK. Oral Pathology: Clinical Pathologic Correlations (6^th edition). St. Louis: Elsevier Saunders; 2012.
• Little JW, Falace DA, Miller CS and Rhodus NL. Dental Management of the Medically Compromised Patient (9^th edition). St. Louis: Elsevier; 2018. 
• Malamed SF. Medical Emergencies in the Dental Office. St. Louis: Elsevier Mosby; 2015.

¹ While adverse drug reaction due to overdose is much more frequent than allergic reaction to local anaesthetics, the oral health professional should assume the patient/client is allergic to the local anaesthetic in question until determined otherwise.
² Hereditary angioedema is a rare genetic condition that results in low or non-functional levels of a blood protein called C1 inhibitor. As a result, swelling can occur in the mouth or throat (which can be potentially life threatening), hands, feet, genitals, and abdomen. Swelling in the gastrointestinal tract can cause extreme pain, nausea, vomiting, and diarrhea. Puffiness of the hands and feet can be painful and interfere with activities of daily living. Warning signs prior to swelling include: extreme fatigue, myalgia, tingling, abdominal pain, hoarseness, and mood changes. Common triggers include minor injury or surgery; stress or anxiety; illnesses such as the common cold or influenza; physical activities such as typing, hammering, or pushing a lawn mower, and certain medications (including some used for treatment of hypertension and heart failure).
³ When antihistamines fail in the treatment of acute or chronic urticaria, corticosteroids (such as prednisone) may be administered. While short course therapy is typical, patients/clients with severe, chronic urticaria may require long-term use of corticosteroids in order to alleviate signs and symptoms. Patients/clients with asthma may also take corticosteroids on an ongoing basis.
⁴ Signs/symptoms of anaphylaxis — which likely will occur within minutes after application, ingestion, or injection of an anaesthetic, medication, or dental product — include: “itching” of the soft palate, shortness of breath, substernal pressure, nausea, vomiting, hypotension, pruritis, urticaria, laryngeal edema, bronchospasm, and cardiac arrhythmias.
⁵ Metals linked to allergic reactions (delayed hypersensivity type) include: mercury (associated with amalgam restoration); nickel (most common sensitizer amongst all metals); chromium; and, to a lesser degree, titanium.
⁶ In the past, iodine-containing disclosing solutions were used, but other dye products (e.g., erythrosine) have replaced these.
⁷ Other clinical examples of type IV cell-mediated (delayed) allergic reactions include infectious granulomas (e.g., resulting from tuberculosis and mycoses), tissue graft rejection, and chronic hepatitis.
⁸ All local anaesthetic agents in the same chemical class (i.e., para-aminobenzoic acid esters [procaine and tetracaine] vs. amides [articaine, lidocaine, bupivacaine, mepivacaine, and prilocaine]) should be avoided. A true allergic response to a pure amide drug is very rare; as a result of their nonallergenic nature, amide-type local anaesthetics are now used almost exclusively for pain control during dental procedures. A reported sulfa allergy precludes use of sulfur-containing local anaesthetics (e.g., articaine).
⁹ In addition to their use in local anaesthetic cartridges (when there is a vasoconstrictor), sulfites are often sprayed on vegetables and fruits to keep them appearing fresh, and they are also included in some canned goods.
¹⁰  C1 esterase inhibitors (e.g., C1-INH concentrate) decrease the number and severity of attacks.
¹¹ Skin testing can help confirm the causative agent. Topical and/or systemic corticosteroids may be used in management.
¹² A minority of cases of aphthous stomatitis may be allergy related.
¹³ including topical antimicrobials, corticosteroids, and eugenol (clove oil)
¹⁴ Skin testing can help confirm the causative agent. Topical and/or systemic corticosteroids may be used in management.
¹⁵ Carvone is a terpenoid compound in many essential oils, but particularly in the seeds of caraway, dill, and spearmint.
¹⁶ These substances are found in toothpaste, mouthwash, chewing gum, candies, ice cream, and soft drinks. In addition to their use as flavouring agents, these compounds are used at higher concentrations to mask the bitter taste of pyrophosphates in antitartar toothpastes. Other, less common causes of allergic contact stomatitis include: formaldehyde, acrylates used in making dentures, and various metals such as nickel, palladium, gold, and mercury used in dental amalgam.
¹⁷ In general, the specific environment of the oral cavity inhibits hypersensitivity reactions. Salivary cleansing of the mucosa and the high degree of vascularization of the mucosa both reduce prolonged contact with allergens.
¹⁸ A fixed drug eruption is an allergic reaction (Type III hypersensitivity) to a medication in which lesions appear in the same site each time a drug is introduced. The lesions more commonly manifest on the skin than on the mucous membranes; the hands and feet, eyelids, lips, genitalia and perianal areas are common sites. Reintroduction of the offending drug tends to result in more intense eruptions.
¹⁹ Type I hypersensitivity, or anaphylactic type hypersensitivity, is a reaction that typically occurs within minutes after exposure to a previously encountered allergen. Plasma cells produce immunoglobulin E (IgE) as a response to allergen exposure. This newly produced IgE binds to mast cells, causing them to release histamine, which is a biochemical mediatory of inflammation. This results in edema caused by increased permeability and dilation of blood vessels and the constriction of smooth muscle in the bronchioles of the lungs. Type 1 hypersensitivity is responsible for urticaria (hives), angioedema, hay fever, allergic rhinitis, bronchospasm (i.e., atopic asthma), localized anaphylaxis, and generalized (systemic) anaphylaxis. Anaphylaxis can be life-threatening, because the patient/client may not be able to breathe due to swelling of oropharyngeal tissue and constriction of the bronchioles – this requires immediate treatment with epinephrine. Medications that suppress inflammation, such as antihistamines and corticosteroids, can reduce signs/symptoms in some forms of type I hypersensitivity. Other types of hypersensitivity reactions are Type II (cytotoxic), Type III (immune complex), and Type IV (T-cell mediated; also known as delayed).
²⁰ In Canada, there are nine priority food allergens; namely, peanuts, tree nuts, sesame seeds, milk, eggs, fish (including shellfish and crustaceans), soy, wheat, sulphites, and mustard. Currently there is no cure for any food allergen; the only way to prevent a reaction is total avoidance of the implicated food. In contrast to a food allergy (which is caused by a reaction of the body’s immune system to specific proteins in a food), a food intolerance is a food sensitivity that does not involve the body’s immune system (e.g., lactose intolerance).
²¹ If a known triggering factor is present, the most effective therapy is avoidance. Urticaria can usually be controlled using only symptomatic treatment with antihistamines (e.g., first-generation agents [which can produce adverse effects, including drowsiness and anticholinergic effects] such as diphenhydramine, hydroxyzine, and chlorpheniramine, or second-generation agents [non-sedating with few adverse effects] such as loratadine, fexofenadine, desloratadine, cetirizine, and levocetirizine).
²² Chronic urticaria is defined as urticaria with recurrent episodes occurring over more than 6 weeks. New-onset urticaria can sometimes be associated with identifiable causes, with the method of exposure (e.g., direct contact, oral or intravenous routes, etc.) being deduced by careful history taking by a clinician. Urticaria results from the release of histamine, bradykinin, and other vasoactive substances from mast cells and basophils in the dermis. [Angioedema results from the release of the substances into the subcutaneous tissues.] In addition to allergen exposure, other causes include infection (including hepatitis [A, B, and C], herpes simplex virus, streptococcal infection, Epstein-Barr virus, and chronic parasitic infections), trauma (i.e., physical pressure), cold temperature, emotional stress, systemic diseases (e.g., systemic lupus erythematosus, rheumatoid arthritis, hypothyroidism, hyperthyroidism, and some leukemias), and pregnancy. Often, though, the cause cannot be identified. While urticaria usually occurs in acute, self-limited episodes, occasionally chronic or recurrent forms occur. Routine allergy testing with a large battery of screening tests is not recommended; however, selected skin allergy test can be performed if food allergy or stinging insect hypersensitivity is suspected. 
²³  In addition to allergic etiology (the most common type), angioedema can also result from infection, trauma, emotional stress, angiotensin-converting enzyme inhibitor drugs (ACEIs [including enalapril, captopril, genzapril, and quinapril] used to treat hypertension), and certain systemic diseases. Often, though, the cause cannot be identified, and there are also rare hereditary forms of angioedema. While angioedema usually occurs in acute, self-limited episodes, occasionally chronic or recurrent forms occur.
²⁴ If a known triggering factor is present, avoidance is indicated. Treatment of angioedema includes antihistamines, corticosteroids, and, in patients/clients with severe signs/symptoms, epinephrine (intramuscular or subcutaneous).
²⁵ Manifestations of laryngeal edema include: swelling of vocal structures and subsequent obstruction of the airway; respiratory distress; exaggerated chest movements; high-pitched sound to no sound; cyanosis; and loss of consciousness.
²⁶ When these signs/symptoms occur on the oral mucosa as a result of direct contact by an allergen, the condition is usually termed allergic contact stomatitis or allergic contact mucositis.
²⁷ Signs/symptoms of Type III hypersensitivity include rash, urticaria, painful joint swelling (i.e., arthritis), renal dysfunction, periorbital edema, and cardiac inflammation.
²⁸ Signs/symptoms of T-cell mediated hypersensitivity in response to topically applied substances include contact dermatitis, contact mucositis, and contact stomatitis.

* Includes oral hygiene instruction, fitting a mouth guard, taking an impression, etc.
** Ontario Regulation 501/07 made under the Dental Hygiene Act, 1991. Invasive dental hygiene procedures are scaling teeth and root planing, including curetting surrounding tissue.