This question comes up in my office almost everyday….should I do skin testing or blood work? As you can see from the response of national experts, it depends. There is NO test that can boast 100% accuracy to predict whether or not you will react to a food. In fact, the gold standard if you will, is still the oral food challenge. Here is some food for thought (really, do you have to pun)
- Clinical history is very important in determining food allergy. If you can eat a food without difficulty breathing, rash, or hives, you are most likely not allergic. You may have a positive test, but that only means you’ve had previous exposure to the food.
- I will often obtain both skin testing and ImmunoCap (blood work) to clarify the presence of IgE-mediated allergy. If both tests are negative, you may have an adverse reaction to a food, not the severe life-threatening anaphylaxis. Very important distinction!
- If in doubt, a food challenge is always a procedure to consider. Here’s why.
- Sometimes the food in question just isn’t worth the trouble to challenge. No one says you have to eat strawberries!
- If you challenge peanuts for example, in the doctor’s office and experience anaphylaxis, better there than at home. Epinephrine is more readily available and in many cases, IV access and full resuscitation is available within minutes of your reaction.
- This is another reason why a single test or treating allergy without experience is not a good idea. Read the link below and tell me just how complicated things can become!
Contradictory skin test and ImmunoCAP results.
Everyday I teach patients the difference between “allergy” and “irritant” reaction. TV ads are overloaded with allergy advertisements in an attempt to sell antihistamines, so why wouldn’t you think that everyone has allergy of some kind. The link below is a question about allergy (anaphylaxis in this case) to chemicals. Consider the following:
- Adverse reactions to pollen, food, chemicals can be divided into “allergy” or “intolerance/irritants“.
- Allergy is defined as the production of IgE to the substance in question. This is why you have positive skin tests and blood testing. Why does this matter?
- You can only be “desensitized” to allergens, not chemicals. IgE can be decreased and if you don’t have IgE to begin with you can’t delete its effect.
- The only treatment for irritants is to avoid them, regardless of whether the substance is a food or chemical.
- For chemical reactions or food intolerance, there’s not much to say except to stay away. Click on the link below just to make sure!
Possible anaphylaxis to chemicals contained in cleaning agents (Dirt Jet Pro/SCRUBS hand sanitizer wipes).
Food allergy is a very common and even popular disease to have. This results in some predictable patient behavior such as:
1. I have allergy based on a blood test only, and I tolerate this food all the time. This may not be allergy at all, but simply a condition called “asymptomatic hypersensitivity”. Relax, some foods you can eat without allergy symptoms even though a blood or skin test is positive.
2. It is fashionable nowadays to have gluten sensitivity. Many patients will perform gluten challenges at home to see if bread or starches make abdominal cramping, skin rashes, or even concentration problems improve or worsen with the offending food. This practice becomes a problem if you are concerned with anaphylaxis (difficulty breathing, low blood pressure) to foods such as peanut, milk, or eggs to name a few. It’s one thing to experience more abdominal bloating after a gluten challenge and a much more dangerous situation to lose consciousness after ingesting peanut.
3. I’m grateful to be a member of the American Academy of Allergy, Asthma, and Immunology (AAAAI) in part because they help me as an allergist to stay current of all the thousands of recommendations published every year on my specialty. One such service is “Ask the Expert” forum and I’d like to share a recent post with you about food challenges.
Here’s the take-home message and the full answer is available if you click on the link below:
1. Food anaphylaxis can be related to the total amount of food ingested. In other words, don’t assume that tolerating a very small amount of peanut will guarantee that you can tolerate peanuts ad lib! Food challenges are performed under close supervision in order to determine HOW sensitive you are.
2. Oral desensitization to foods is still in the research stage and the experts on treating food allergy do not recommend this procedure be performed outside of a research protocol. It only takes one bad outcome to taint any progress made with treatment of food anaphylaxis.
Anyway, it’s lunchtime, and talking about food does make me hungry!
Oral food challenge to peanut.