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Immune System: Could pregnancy have caused my allergy?

I gave birth to twins five months ago and am breastfeeding them. I am 35 and it was my second pregnancy. Two or three times during the pregnancy I seemed to have a reaction to nuts - my lips and tongue swelled. Since the birth, the reaction has got worse, so now I avoid nuts. My doctor said it was to do with my immune system being altered by pregnancy, but will this allergy stay with me? And does this mean one of my babies might have an allergy of some kind?

Dr Fred Kavalier answers your health question:

Pregnancy has a powerful effect on the immune system, but the effect on allergies is difficult to predict. About one-third of women who have allergic conditions, such as asthma, get better during pregnancy. But one-third get worse during pregnancy. The hormones of pregnancy are one of the factors that affect the allergic response. But there are also fundamental changes in the immune system that allow a woman to carry a baby without her body rejecting it. The reaction you are getting to nuts does sound like a genuine food allergy. Swelling of the tongue and lips is potentially serious, and you must take great care to avoid the nuts that are causing this reaction - a further exposure to nuts could produce a more dramatic reaction. I doubt the allergy will go away when you stop breastfeeding. It is unlikely that either of your twins will have the same allergy, although it is impossible to predict if they will be allergic to something else later in life. Breastfeeding is thought to provide children with some protection against allergies, but there are many breastfed children who do develop allergies.

Please mail your questions for Dr Fred to health@independent.co.uk. He regrets that he is unable to respond personally to questions.