Allergies and eczema: Are they related?
© 2014 Roy Benaroch, MD
Theresa wrote in, “I’d be interested in seeing an article about the connection (or lack thereof) between food allergies and eczema. Also interested in the helpfulness (or lack thereof) of large blood panels for food allergy testing.”
Two good topics—and I’ll get to food allergy panels in the next post. First: What’s the connection between allergies and eczema?
Eczema is by far the most common chronic skin condition pediatricians see. It’s present in about 1 in 3 young children, or maybe more if you count the milder cases. In fact, if you look closely enough, just about every child has at least some eczema. It’s usually mild, and improves nicely with good skin care and the occasional use of low-strength topical steroids.
What causes the itchy, scaly, red rash? Many things seem to contribute: dry skin, rough fabrics, and scratching all make eczema worse. It often runs in families, and often occurs in the same children who later go on to have allergic rhinitis (hay fever), asthma, and food allergies (those conditions, as a group, are called “atopic.”) Eczema is also called “atopic dermatitis”—atopic referring to inflammation and sensitivity, typically caused by an allergic trigger. These conditions are all interrelated, and often co-exist. So is eczema, the rash, caused by a specific, identifiable, and avoidable allergic trigger?
There’s the controversy. If you ask allergists, they’ll say “probably yes.” They stress identifying and avoiding specific triggers, typically one or more foods. Sometimes their advice is guided by allergy testing, or sometimes just by history, and sometimes by trial and error. Just avoid food X, and if that doesn’t work, avoid food Y. If there is an allergic food trigger, it’s probably one of the common food allergies, like egg, milk, wheat, soy, fish, or peanut. Maybe try avoiding those.
But it’s hard to avoid all of those foods—and “testing” will often lead to false positive or negative results. If food allergy does trigger eczema, it does it slowly, so it may take several days or weeks of restrictions and reintroductions of multiple, overlapping foods to figure this out. Meanwhile, Junior is still itchy. So the dermatologists take a different approach.
If you ask dermatologists if eczema is caused by food allergy, they’ll say “probably no.” They stress taking care of the skin (using good bathing techniques, moisturizers, sometimes topical antiinflammatory medications, and sometimes agents to reduce bacterial colonization.) Just treat the skin, that’s the dermatologists’ motto. We can make this better, and quickly, without anyone going hungry.
Now, if you ask pediatricians if food allergy causes eczema, we’ll say “sometimes.” Though some of us are probably more allergy-focused than others, most of us probably favor practical advice: for mild-to-moderate eczema, it’s usually best to focus on good skin care, and treat the eczema, and get Junior feeling better. IF initial, safe therapy doesn’t work, or if the eczema is severe, then we’ll also try to identify food triggers—though we’ll keep up the good skin care at the same time. One approach doesn’t mean you can’t also follow the other. And, in fact, the best dermatologists and allergists will also recommend this kind of middle-of-the-road, practical advice.
What about those food allergy panels Theresa asked about? Short answer: They don’t work, at least not if your goal is to figure out what your child is allergic to. More in the next post.