Pediatrics - Allergies

Pediatrics

[ALLERGIES]

Intro When discussing allergies, we’re generally referring to IgEmediated type 1 hypersensitivity. This will be basis of the majority of the conditions covered. For review, the full gamut of hypersensitivity reactions is briefly stated to the right.

Type 1 Type 2 Type 3 Type 4

IgE-mediated Cytotoxic, Antibody-mediated Antibody:antigen complex Delayed T-cell mediated reaction

Anaphylaxis Hemolytic anemia Serum sickness Poison ivy

Acute Allergic Presentations

Anaphylaxis The dreaded complication of IgE-mediated allergic reactions, this can be life-threatening. It can involve multiple organ systems including: cardiovascular (hypotension), gastrointestinal (diarrhea), skin (hives), and pulmonary (airway edema). Anaphylaxis requires involvement of at least two organ systems; it doesn’t need to involve the airway. A confirmed exposure to an allergen isn’t always needed. Treat with epinephrine (1:1,000 IM), support the airway with intubation, and blood pressure with IV fluids and pressors if needed. Adjunctive therapy includes H1/H2 blockers  and albuterol - they have more supporting evidence than steroids. Provide an epinephrine pen at discharge and advise staying away from allergic triggers. Urticaria This is the skin manifestation of allergic reactions. It’s usually IgE-mediated (type 1 hypersensitivity) but can also come from agents that cause non-immunologic mast cell degranulation (contrast, opiates, Red man syndrome from vancomycin). The skin will have erythema and wheals which are often pruritic and limited to superficial layers of dermis. Always check for signs/symptoms of anaphylaxis (dyspnea, wheezing, GI symptoms, etc.). To treat, use 2nd generation H1 antihistamines (cetirizine, loratadine, fexofenadine) and remove/avoid the offending agent  (if possible). 1st generation H1 antihistamines can be used but have the side effect of sedation. Additional therapies such as H2 blockers, leukotriene antagonists, and steroids have a limited role; they’re typically reserved for more chronic causes of urticaria. Angioedema Similar to urticaria but the swelling often involves deeper layers of the dermis and mucous membranes (which include lips, airway, and GI tract). Learn these as independent of histamine (this is debatable). It can be seen with urticaria, as part of anaphylaxis, or completely independent (think of ACE-inhibitor reactions). As with urticaria, screen for anaphylaxis but typically treatment is aggressive given concern for airway edema. Secure the airway, with intubation if needed. Time will get them through this. If there’s concern for hereditary angioedema, C1 inhibitors can be administered, but the safe bet (from an availability perspective) is FFP.

Clinical diagnoses have significant overlap - Need exposure (can be known for suspicion for) - Need two+ organ systems involved: Skin/mucosa  Respiratory  Hypotension or end-organ d ysfunction (syncope) GI symptoms

Check for presence of anaphylaxis! Treatment: - Removal of offending agent (if possible) - 2nd generation H1 antihistamines - Additional therapies have limited role

Compared to urticaria, angioedema has deeper involvement of tissue and potential for mucous membrane involvement. Check for evidence of anaphylaxis or airway involvement! Treatment: - Removal of offending agent (if possible) - Intubate - H1/H2 and Steroids probably don’t work - FFP if hereditary angioedema!

© OnlineMedEd. http://www.onlinemeded.org

Pediatrics

[ALLERGIES]

Chronic Allergic Conditions Many of these conditions are often together in some combination. As such, note that there’s a significant overlap in therapy.

Asthma This is covered extensively elsewhere so we won’t address it here. Just know that there can be a significant allergic component involved. Allergic Rhinitis An IgE-related inflammation of the nasal mucosa. Time to develop a sensitivity and late environmental exposure are two factors needed to produce disease. Presenting symptoms include rhinorrhea, sneezing, and nasal itching. Precipitating factors can  be seasonal   (grasses, weeds, outdoor mold) or perennial  (pets, dust mites, indoor molds). There are several physical exam findings you may be tested on (which are useful in real life as well). Starting with the face, venous congestion underneath the eyes (known as “allergic shiners”) or a transverse nasal crease (“allergic salute”) from excessive upward wiping of the nose are often seen. The mucosa of the nose can be pale and boggy and polyps may be present in older children. The posterior oropharynx may have cobblestoning  as a consequence of post-nasal drip. Diagnostic testing usually isn’t needed  as 1) environmental history can uncover causes and 2) identification of specific antigens may not change management unless immunotherapy is considered. Treatment includes allergen avoidance  (dust mite  bed covers, animal removal), intranasal medications  (steroid, antihistamines), oral medications (antihistamines, leukotriene antagonists), and immunotherapy (in severe or refractory cases). Allergic Conjunctivitis Often seen concurrently with allergic rhinitis, the mechanism and triggers are exactly the same as noted above. Symptoms include ocular pruritus, redness, and discharge. Look for eye discharge, conjunctival redness (injection) and swelling (chemosis), and “allergic shiners.” Treatment involves avoid of allergens (shocker!), artificial tears (provides barrier), medicated eye drops  (combinations of mast cell stabilizers and antihistamines), as well as oral medications (2nd generation H1 antihistamines). Immunotherapy can also be given consideration as well. Atopic Dermatitis Typically seen in younger children, it appears as scaly skin on the extensor surfaces  (infants/young children) or flexor surfaces (older children and adults). The skin can be pruritic and become secondarily infected  if severely excoriated. Causes can be related to environmental exposure or food ingestion. Use emollients and moisturizers as baseline therapy. Topical steroids can be used as first line for exacerbations.

 Precipitating facto rs can be seasonal or peren nial  Key exam findings: - Allergic shiners - Allergic salute - Pale/boggy nasal mucosa - Cobblestoning of posterior oropharynx  Diagnostic testing - Skin testing is usually first line - Serum testing (RAST) may overcall allergens

Treatment preferences: - Allergen avoidance is key - Intranasal corticosteroids are the MOST effective - Intranasal antihistamines are also considered 1st line - Oral antihistamines (2 nd  > 1 st  generation) frequently used +/- leukotriene antagonist  Immunotherapy has unclear magnitude of effec t

Treatment: - Avoid triggers - Combination eye drops (mast cell stabilizers + antihistamines) - Oral antihistamines (especially if allergic rhinitis component)

 Beware of high potency ste roids in areas of thin skin (such as the  face) as this can cau se further thinning.

© OnlineMedEd. http://www.onlinemeded.org

Pediatrics

[ALLERGIES]

Food Allergies See association with atopic dermatitis. Reactions can be varied. They can be as mild as oral or cutaneous pruritus, as bothersome as vomiting and diarrhea, or as severe as anaphylaxis  (see prior heading). Typical triggering foods include wheat, eggs, soy, milk, tree nuts, peanuts, shellfish, and finfish. About 85% will outgrow allergies to wheat, eggs, soy and milk while the nut  and fish allergies are fairly persistent. The best way to treat is to avoid the offending food. An epinephrine pen can be provided if the symptoms result in anaphylaxis. Of note, this can occur in breast feeding infants; in that scenario the offending formula (or food in mother’s diet if breastfeeding) should be avoided.

Common food allergies: - Wheat - Soy - Milk - Eggs - Nuts (tree nuts and peanuts) - Fish (shellfish and finfish)  Avoidance is the ma instay of treatment!

Milk-Protein Allergy A subset of the above, it’s seen in children around 6 months of age. Symptoms such as feeding intolerance, vomiting, failure to thrive, and bloody stool  will be the tip-off. There’s crossreactivity with soy. Treat by avoiding cow’s milk protein until 23 years of age. Use hydrolyzed formula in the interim. Insect Sting Allergy Local reactions (erythema, edema) are most common. Remove the stinger without grasping the venom sac. Optionally treat with local cold compresses. Treat anaphylaxis (see prior heading) if  present and provide epinephrine pen i f needed.

© OnlineMedEd. http://www.onlinemeded.org