Updated December 29, 2014.
Written or reviewed by a board-certified physician. See About.com's Medical Review Board.
The food you eat affects every part of your body. If you have food allergies or sensitivities, your body's response may interact with or worsen other conditions you have. Managing your food allergies effectively may help you to also manage other conditions.
While researchers still do not understand all of the ways in which food can affect our bodies, minds, and moods, they do know some things about how food allergies and sensitivities can interact with the following conditions:
ADD/ADHD
Type "ADD diet" into a search engine and you will be flooded with websites offering miracle cures to attention deficit disorder through food. Very few of these diets have any research to back them up, and there is little research on the interaction of food allergies or sensitivities and ADD/ADHD.
Researchers reviewed studies from the 1970s to the present that looked at special diets and their impact on ADD symptoms. They found that most children with ADD do not experience significant improvement on any special diet -- not gluten-free, not Feingold, and not low-sugar. However, for children who have both ADD and diagnosed food allergies, the results may be different. One study found that 90% of children with both allergies and ADD reacted to a challenge of artificial food coloring.
Eating a balanced diet and avoiding the peaks and crashes that come with too much refined sugar may help children with ADD to focus, just as it does for all children.
Asthma
Asthma is an allergic disorder, as are food allergies.
People with both asthma and food allergies are at a higher risk of severe allergic reactions, or anaphylaxis. If you have both, you should carry emergency medication and wear a medical ID at all times.
Asthma that is solely triggered by food is rare. However, you may have asthma that is triggered by pollen or pollution as well as food. Oral allergy syndrome, in which people with pollen allergies react to certain fruits and vegetables, may trigger an asthma attack.
Autism
We still do not know the cause, or causes, of autism, although some researchers believe that the immune system plays a role. Some studies have found that women who have psoriasis, asthma, or environmental allergies have a higher risk of having a child with autism. The linkage between a mother's allergies and a child's brain development is not clear.While many children with autism suffer from gastrointestinal (GI) problems, only some find a benefit from gluten-free, casein-free diets or other diet modifications. It is not clear why special diets help some children on the autism spectrum and not others.
Depression
Those of us with allergies have long been aware that our mood is linked to our allergy symptoms. Researchers are beginning to understand the mechanism behind this.
Cytokines, proteins released by mast cells during an allergic reaction, cause inflammation that makes you feel lousy. In addition, the cytokines may reduce the level of serotonin your body produces. Serotonin helps to regulate mood. So even after your allergic symptoms have gone away, your mood may be dampened.
Eczema
About one-third of people with eczema will test positive for at least one food allergy. Eczema is a complex problem and can be triggered by environmental factors, such as lotions or soaps, pollen allergies, or even stress.
If your child has severe eczema, your doctor may recommend allergy testing to see if food or other allergies are part of the cause.
Irritable Bowel Syndrome
Irritable bowel syndrome (IBS) is a chronic condition that is characterized by frequent abdominal pain that is relieved after a bowel movement. Many people with IBS feel that their symptoms are worse after eating certain foods.
There may be a link between food allergies and IBS. While IBS symptoms are not traditional food allergy symptoms, researchers have found higher levels of mast cells in the GI tracts of people with IBS. Other studies have found that people with IBS have higher rates of pollen allergies. Oral allergy syndrome may play a part in IBS.
Pollen Allergies
Pollen allergies may trigger food allergies if you have oral allergy syndrome (OAS). If you find that eating certain raw fruits and vegetables causes your mouth to itch or swell during pollen season, you may have OAS.
In the threshold theory of allergies, each person has a certain level of tolerance of an allergen, and they do not experience negative symptoms if they remain below that. If you imagine a cup that is almost full of water, pouring more water into the cup will cause it to overflow. This is what happens when you eat an apple during pollen season -- because your body is already coping with other allergens, the addition of the apple pushes you over the edge to an allergic response. At other times of year, you may be able to eat an apple without a reaction.
Migraines
Migraine headaches have been linked to eating foods containing tiramine, and in some people, histamine intolerance. Histamine and tiramine occur naturally in foods such as red wine, aged cheeses, and preserved meats. A sensitivity to histamine or tiramine is not a traditional food allergy, but it may cause similar symptoms such as hives, diarrhea, eczema, or even anaphylaxis.
If you suspect that your headaches are triggered by certain foods, you can try eating a "headache diet" that avoids aged and fermented foods. Talk to your doctor if you suspect that you may have a histamine intolerance.
Sources:
Croen LA, Grether JK, Yoshida CK, et al. Maternal Autoimmune Diseases, Asthma and Allergies, and Childhood Autism Spectrum Disorders. Arch Pediatr Adolesc Med. 2005; 159:151-7.
Maintz, Laura and Natalija Novak. "Histamine and Histamine Intolerance." American Journal of Clinical Nutrition. May 2007, 85(5): 1185-96. 8 June 2008.
Millichap, et al. The Diet Factor in Attention-Deficit/Hyperactivity Disorder Pediatrics, peds.2011-2199
Tobin MC, Moparty B, Farhadi A, DeMeo MT, Bansal PJ, Keshavarzian A. Atopic Irritable Bowel Syndrome: A Novel Subgroup of Irritable Bowel Syndrome with Allergic Manifestations. Ann Allergy Asthma Immunol. 2008;100:49-53.
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