I have been wanting to write about food allergy desensitization for a long time. It's a huge subject, and nothing has proven to be a true cure for food allergies or intolerances, but it's an important discussion. Today we'll focus on the classic oral desensitization with sublingual drops.
Many conventional allergists use sublingual drops to treat classic food allergy symptoms such as anaphylaxis. Today I was reading a couple of medical articles on this topic which gave me food for thought (and for blogging), and I will use some statements from these articles to help explain the benefits and limitations of oral desensitization.
Oral desensitization is the process of placing diluted amounts of an allergen under the tongue. The theory is that these small amounts will help train the immune system to not over-react to the allergen. This is an especially important concept for people with anaphylactic reactions, which can be life threatening.
Although this treatment is commonly found in the typical allergy office, it is not universally accepted, nor is it universally successful. However, it does seem to work in some cases. But what does "work" really mean?
To quote from one of the articles,
allergen specific immunotherapy may offer new perspectives for the management of patients at risk of potentially fatal reaction to foods. ... protecting the allergic subject from anaphylaxis caused by accidental ingestion of small food amounts. (1)
This is of course very important for people suffering from these types of allergic reactions. But it is not necessarily the same thing as completely eliminating the allergy. This is a topic of great confusion in allergy medicine (or in any area of medicine), where treating the symptoms is often inaccurately portrayed as curing the problem. To emphasize this point, read another quote from the second article that I read today:
Oral immunotherapy studies continue to show promise for the treatment of food allergy, but determining whether the treatment causes tolerance (cure) or temporary desensitization remains to be explored. (2)
Here they can't stop themselves from throwing in the word cure. However, tolerance is not the same things as curing the problem. In fact, the word tolerance implies that you are tolerating the problem, not that you've cured it. This is true regardless of what you are tolerating. Just try it in a sentence. "I am tolerating my noisy neighbors." You haven't cured the problem, but you're adapting as best you can. It's better than the alternative, which is over-reacting, but it's not the same as having them go away never to be heard from again.
It's the same thing for allergies. The patient no longer has an anaphylactic reaction, which is fantastic. But there is no evidence that they no longer have any type of immune reaction. They are still likely getting inflammation, but it's more tolerable. And what the article really should have stated was that "...determining whether the treatment causes permanent relief from anaphylaxis or temporary desensitization remains to be explored."
I have yet to see studies on oral desensitization demonstrate with blood testing that the patient no longer has an IgE reaction at all, or that it impacts all potential allergic reactions.
As you can see, it's an interesting subject, but one that still has a lot more questions than answers. And unfortunately there is no evidence that it has any relevance to gluten intolerance or other related types of food allergies and intolerances.
1. Recent Pat Inflamm Allergy Drug Discov. 2010 Jan 26. [Epub ahead of print]
Anaphylaxis: An Update on its Understanding and Management.
Incorvaia C, Mauro M, Pravettoni V, Incorvaia S, Riario-Sforza GG.
2. Journal of Allergy and Clinical Immunology. 2010 Jan;125(1):85-97.
Advances in allergic skin disease, anaphylaxis, and hypersensitivity reactions to foods, drugs, and insects in 2009.
Sicherer SH, Leung DY.
4 comments:
The sublingual approach is much safer than oral therapy since the amount of antigen is much less yet it is applied to a more immunologicly active area, the mucosal surface under the tongue. There are few mast cells, eosinophils or basophil there yet there is a high density of dendritic cells and T-cells which promote immunologic tolerance.
Oral therapy has a significant risk of acute allergic reaction yet may not induce regulatory T-cells the way sublingual immunotherapy is known to.
It would be bad form to cause anaphylaxis when a safer effective technique is available. Oral therapy or injection therapy for foods have a known risk of severe reaction, sublingual is safer, less expensive, and works very well in even the most sensitive patients.
If you are serious about trying oral therapy you may want to look up Lyndon Mansfield's abstract for peanut oral immunotherapy from the 2009 ACAAI meeting in Miami. There was some benefit but also a systemic reaction easily treated with epinephrine.
I came many times across the term "hypersensitivity threshold".
What are the thoughts on that? thank you
The hypersensitivity threshold of a food allergy is the amount of the food required to trigger a symptom. Studies sometimes attempt to establish such a threshold. In reality individual people are different. Some people respond to a tiny amount of the allergen, and others require a larger dose. But generally the hypersensitivity threshold is a very very small amount the food.
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