2017 – PAGE 90-91 – ALLERGY & IMMUNOLOGY
HAY FEVER, FOOD ALLERGIES, AND ALLERGIC RASHES
Hay fever due to pollen takes a few years to develop. So if a child less than 3 years of age presents with rhinitis, consider other diagnoses.
- Ragweedfrequently causes Respiratory symptoms along with the usual sneezing, allergic conjunctivitis, rhinitis, and tearing of hay fever.
- Treatment options include oral antihistamines, intranasal antihistamines and intranasal steroids.
The differential for chronic rhinitis includes HAY FEVER, SINUSITIS, CYSTIC FIBROSIS, FOREIGN BODY, a nasal POLYP, and VASOMOTOR RHINITIS.
Triggers for vasomotor rhinitis may include emotions, cold wind, change in temperature (or humidity), and pollution. Typical environmental allergens are NOT triggers.
SKIN TESTING = AEROALLERGEN TESTING
- FALSE negatives can occur when patients are on antihistamines or antidepressants!
- NEGATIVE PREDICTIVE VALUE: NPV of skin testing for foods or inhalants is excellent.
- POSITIVE PREDICTIVE VALUE: PPV is good for inhalants but not good for foods.
PEARL/SHORTCUT: All skin-testing results should be considered fairly reliable, regardless of whether they are positive or negative (for food, aeroallergen, or inhalant), the one EXCEPTION being a POSITIVE skin-testing result for food allergies.
About 50% of patients with hay fever respond to immunotherapy. There’s a 0.5% chance (1 in 200) of having a severe reaction during therapy. If it happens, it will usually occur within 30 minutes, and will usually occur during peak pollen seasons or within the first year of immunotherapy (the rapid build-up phase).
Since radioallergosorbent testing (RAST) is IN VITRO (blood) testing, it is NOT affected by taking antihistamines.
When dealing with children with a strong family history of allergies, or who already have signs of atopy, it is suggested that parents introduce highly allergenic foods at home with oral antihistamines on hand, and starting with only a single taste. Evidence does not support delaying the introduction of allergenic foods such as peanuts and shellfish.
ABDOMINAL PAIN may be the only sign of impending anaphylaxis. If the patient has a history of a food allergy, GIVE IM EPINEPHRINE.
- PEARL: After an exposure, symptoms may continue to EVOLVE even up to two hours later. It is highly unlikely that the ONSET of an allergic response will start two hours after the food exposure.
- INFANTS/TODDLERS: Allergies to eggs, milk, soy, or wheat are common. Children will usually outgrow these by 5 years of age.
- OLDER CHILDREN: Allergies to shellfish and peanuts are common and are less commonly outgrown.
PEARL: There is NO contraindication to giving contrast in kids with a shellfish allergy. Just give it. No need to pre-treat.
Although peanuts are legumes, for patients with a peanut allergy you do not need to recommend against exposure to all legumes. Instead, caution against exposure to TREE NUTS since they are often processed in the same factories as peanuts, and because there is a 25%-50% likelihood that these patients ALSO have a tree nut allergy.
PEARL: “Peanut” is a misnomer because it is not a tree nut. Most tree nuts have the word NUT in them (e.g., hazelnut, macadamia nut). Legumes typically have the word BEAN in them (e.g., black bean, fava bean, lima bean). Don’t get confused on the peds boards.
Foods like spicy foods and beans may be associated with abdominal discomfort ± flatus. These reactions should not be classified as allergies.
In babies, atopic dermatitis (eczema) SPARES the diaper folds/flexural surfaces (but not in older kids). It is PRURITIC and LICHENIFIED. Food allergies CAN exacerbate eczema. Breastfeeding x 6 months or using hypoallergenic formula may delay the onset of eczema but does not reduce its incidence. The contribution of early food ingestion to the development of atopic dermatitis is controversial. Eggs, fish, milk, peanut, soy, wheat and strawberries are the foods thought to possibly contribute, but delaying their introduction doesn’t help. Positive skin and RAST tests for foods are not predictive, either. Treatment options include emollients and topical steroids. Avoid use of steroids in areas where the skin is thin. Use the lowest potency steroids that work. Watch for superinfection if the eczema is not improving with appropriate therapy.
Urticaria (hives) refers to a skin rash usually consisting of pale red, raised, itchy bumps. It might be associated with burning or stinging and is frequently caused by an allergic reaction, though there are also nonallergic causes. Most acute cases (lasting hours or less than 6 weeks) are due to the result of an allergic trigger. If urticaria is noted as an isolated skin manifestation (with or without angioedema), you do NOT have to administer epinephrine. You MUST give epinephrine if there is also ANY breathing-related symptom to suggest anaphylaxis (coughing, wheezing or any evidence of airway compromise). Such cases should be referred to an allergist because of the possible need for venom immunotherapy.