Food intolerance (adverse reactions) may be due to allergic or non-allergic cause. However it may be hard to distinguish the two. The symptoms are eczema, hives, gastrointestinal complaints and rarely rhinitis and asthma. Allergic reactions occur immediately (in a few minutes or hours) and caused by IgE mediated mechanism as demonstrated by positive skin test or ImmunoCAP specific IgE blood test. In contrast non-allergic reactions tend to occur late (in hours to days) and the skin test and ImmunoCAP specific IgE blood test are negative.
FPIES(food protein-induced enterocolitis syndrome) is a non-allergic GI disorder that present in infancy with severe vomiting and diarrhea. The most common food triggers are cow milk, soy formula, and even solid foods including rice.
Eosinophilic Eosphagitis is a condition with both allergic and non-allergic (delayed hypersensitivity) components. Symptoms are swallowing difficulty, food impaction, and heart burn. The diagnosis is made by esophageal biopsy showing more than 15 eosinophils per high power field. The symptoms improve when patients go on a restriction diet of 6 common foods (milk,egg, soy, wheat, nuts, and fish)
The true incidence rate of food allergies is lower than reported by patients ( ~8 % in children and ~1% in adults). Unfortunately the incidence rate has been rising recently. So is the mortality rate from food anaphylaxis.
The most common foods associated with food allergy are;
For young children: milk, egg, soy, wheat, peanut
For adults: shell fish, peanut, tree nuts, fish, milk, egg
Common Allergic Foods
- Cow Milk
- Two major proteins are casein and whey
- 85% outgrow by 3 yrs of age
- 30% of children with + ST to milk at 1 yr develop other food allergies
- Lactose intolerance may be confused with milk allergy
- Cow milk shares allergen with goat milk
- For cow milk sensitive infants, milk protein hydrolysate formula is a better choice than soy milk
- Egg
- Egg white is more allergenic than yolk
- Present in mayonnaise, glossy baked goods, pound cakes
- Flu vaccine-yes. MMR-no
- Most out grow by 5 yrs
- Soy
- 10% of milk allergic children also sensitive to soy
- Soy milk, powder, tofu, green soybeans
- 6/7 soy lecithin contain soy protein
- 3/8 soy oil preparation contain soy protein
- Peanut (Ground Nut)
- Affect 0.6% of U.S. population: ~ 1.6 million
- 150 die per year: 50% of food related fatality. Often due to accidental exposure
- Powder can cause symptoms. Smell-unlikely
- Only a minority may grow out of it
- If RAST > 15 KU/L ; permanent
- < 15 KU/L: may grow out
- Tree Nuts
- Tree nut protein is not related to peanut
- But 1/3 of peanut sensitive children may develop sensitivity to tree nuts independently
- Almond, walnut, cashew, pecan, pistachio
- Sesame seeds are related to tree nut protein
- Shell Fish
- The most common allergic food for adults
- Mollusks (oyster, clams, oysters, squid)
- Crustacea (shrimp, lobster, crabs)
- Topomycin is the responsible protein
- Dr. Song can order “ shell fish RAST panel”
Diagnosis
Skin Test:: If negative, food allergy is unlikely (95%). If positive, only 30-50% may have real manifestation when challenged with the particular food.
Rast (radio-allergo-sorbent test): The test measures the amount of IgE antibodies to particular foods in the blood. This test is much more reliable than the skin test in predicting food allergy symptoms. However, the test is not sensitive enough to be used as a screen tool.
If the IgE levels are above the following value, the patient has greater than 95% chance of experiencing an allergic reaction.
Egg-7 (kUa/L). Milk-15. Peanut-14. Fish-20. Tree nuts-15.
If the IgE levels are above the following value, the patient has greater than 75% chance of experiencing an allergic reaction.
Soybean-30 (kUa/L). wheat-26
Component Tests
Allergy causing food proteins can be broken down to different components (epitopes). Allergic (IgE) reaction to some components may be more predictive of real clinical reaction than other components. A good example is peanut allergy; a component known as ‘Ara h2 ‘, increased response to which is predictive of more severe reaction than other components such as ‘Ara h8’. This test can be ordered now through Dr.Song’s office (may not be covered by insurance)
Food Challenge
Even when skin test is negative or rast value is low, patient may, in rare instances, experience allergic symptoms. Therefore it is necessary that patient be put to test with real foods. This can be done in our office before the patient tries the food at home. If the patient reacts to the food adversely in the office, he/she may be treated. It takes usually ~ 3 hours to perform the test since the amount of the challenge food is increased incrementally.
Prognosis
Most infants tend to grow out of milk and egg allergy.
Most children do not grow out of peanut or tree nut allergy. But some do when they have low level of RAST.
Treatment
- Avoidance of known allergenic foods
- If foods are suspected as a cause for clinical symptoms, but patient and doctor cannot pin point it, one may try an elemental diet . See below
- Epinephrine with accidental ingestion of an allergic food when respiratory difficulty occurs or when there is history of anaphylaxis. Keep Epipen at a reachable location at all times. Learn how to administer it.
- Antihistamine (benadryl is preferred since it acts faster) whenever accidental ingestion occurs.
- Prednisone (15 mg to 40 mg ) to prevent delayed reaction.
An example of elemental diet
For infants: amino acid powder such as Vivonex or Neocate may be tried.
For Adults:
Rice, puffed rice, rice flakes, rice krispies
Pineapple(canned), apricots(canned),
Cranberries,peaches, pears, apples : fresh or juice/nectar of these
Lamb, chicken
Asparaguss, beets, carrots, lettuce, sweet potato
Tapioca
White vinegar, olive oil
Honey, 2oz a day, cane sugar, salt
Neocate, Vivonex
Prevention
- Restrictive Perinatal Diet
- Various large scale studies show
- Restrictive diet (no milk, egg and peanut) during pregnancy- No benefit to infants
- Restrictive diet to infants during the 1st year (Breastfeeding for 6 months + introduction of potential allergenic foods after one year); Beneficial to infants> decreased the incidence of atopic dermatitis (eczema) during the fist one year of life. But no effect on the development of asthma or hay fever
- When dining out
- Ask about ingredients and the way food is prepared before you order when you dine out.
- Order simple prepared foods such as baked potates, steamed vegetables, and broiled meat.
- Avoid creamy sauces and toppings.
- Avoid buffet salad bars. Often people will use the same spoon in different dishes.
- Asian, Thai, and African foods often contain peanuts.
- Peanuts can be finely chopped and baked in cakes and pie crusts.
- When traveling
- Get a letter from your allergist that confirm food allergy.
- Bring your own food.
- Confirm your peanut-free snak request at the gate and ith the lead flight attendant.
- Prepare for the unexpected. Bring Epipen and antihistamines.
- West Bracelet: MedicAlert: 2323 Colorad Ave. Turlock, CA 95382. 800-432-5378
- Useful web links
- American Academy of Allergy of Asthma and Immunology (AAAAI). Phone: 414-272-6071. Fax: 414-272-6070. www.aaaai.org
- Food Allergy Network (FAN): Phone: 703-691-3179. Fax: 703-691-2713. www.foodallergy.org
