ADHD and Allergy: Is There a Link Between the Two?
A recent study provided evidence for an association between Attention Deficit Hyperactivity Disorder (ADHD) and allergic diseases. I found the report very interesting because for years parents have asked me if their child's ADHD is caused by food or environmental allergies. Hundreds of times I replied by explaining that ADHD and allergy are two very common entities that have separate mechanisms and causes. I would go on to say that both have their own treatments and need to be addressed, but allergy testing to foods and environmental triggers is not indicated if there are no signs or symptoms of environmental or food allergy.
The study I reviewed, which prompted this posting, did not change how I answer the above question. That said, the increased association of ADHD and allergy brings more thought to caring for patients with either one of these disorders because both have been associated with delays in diagnosis, and some allergy medications may complicate the treatment of ADHD.
ADHD is a very common childhood disorder which may continue well into adulthood. The average age of onset is 7 and about 9 percent of American children between 13 and 18 years have ADHD. Symptoms include difficulty staying focused, paying attention, controlling behavior and over-activity. There are sub-types of ADHD which do not include hyperactivity (over-activity). These children are often diagnosed after years of demonstrating other signs of the disorder but ADHD had not been considered because the child was not hyperactive. The cause of ADHD is uncertain but genes are thought to play a significant role. Scientists think a combination of genetic vulnerability and environmental factors (such as tobacco smoke exposure or lead or some food additives) may cause this disorder.
Food allergies have been reviewed many times over the years on this website. The most common food triggers in children are milk, egg, peanut, wheat, soybean, fin fish and shellfish. Food allergy reactions may include: itching of the mouth, throat or skin; hives or swelling of the tongue, throat, face or other parts of the body; cramping abdominal pain, diarrhea and bloating; flare-ups of eczema, or full blown anaphylaxis (the most severe of allergic reactions).
This British study evaluated 884 boys who had the diagnosis of ADHD and were on medication to treat it. Each case was matched to 4 other boys who had no history or treatment of ADHD.
The investigators reported increased asthma, impetigo (a skin infection often associated with allergic eczema) and use of antihistamines in the ADHD group compared to boys who didn't have this disorder. There was softer evidence for increased milk intolerance, use of respiratory and topical steroids antifungal and antibacterial agents in the ADHD group.
What Does This Mean?
This study further supports a link between allergic disorders and ADHD although it does not provide evidence for the cause or mechanism of the relationship. Are children more likely to have ADHD because of their allergy genes, or is it the presence of ADHD in their genetic makeup that leads to more allergic problems? We really don't know at this point. The diagnosis or suspicion of ADHD alone does not mean allergy testing should be ordered. On the other hand, children who have ADHD and in addition, respiratory, skin or food allergy symptoms should be evaluated for allergy testing since the likelihood of positive results is higher.
Moderate-to-severe nasal allergies and asthma are often associated with sleep loss, daytime fatigue and lack of attention. ADHD can be much harder to manage in this setting. Furthermore the medications used to treat allergies may amplify the problem.
Some allergy medications may complicate the management of ADHD related to adverse side-effects and/or drug interactions.
Pseudoephedrine (PSE) is a popular nasal decongestant which may have side effects of tremor, agitation, irritability, increased heart rate, insomnia and palpitations. These potential adverse effects may worsen
ADHD, as well as interact with some medications used for treatment of ADHD. PSE containing drugs have warnings about being taken with other stimulants. Many drugs used to treat ADHD are in fact stimulants.
What Can You Do?
Look out for signs or symptoms of allergy in your child if he/she has ADHD. Get your child evaluated for allergies if this is the case. Proper and careful management of their allergic problems may help them better respond to treatment of ADHD. Frequently review all medications including OTC drugs to look for risks of undesirable side effects or drug interactions. Continue to read postings on this site and HealthCentral's section on ADHD.
Are both conditions being addressed?
Ann Allergy Asthma Immunol. 2013;111:102-106.