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Understanding Food Allergies

Have you noticed food allergy warnings at restaurants? Maybe you’ve heard about peanut-free classrooms and flights. People who have serious reactions to certain foods must be careful about what they eat, and what others eat around them. There’s no cure for food allergies. But researchers are learning more about how to prevent and treat this condition.

Allergic reactions happen when your immune system‐your body’s defense against germs and foreign substances‐overreacts to something that’s normally harmless. In the United States, most food allergies are caused by peanuts, tree nuts, fish, shellfish, eggs, milk, wheat, and soy. Allergies show up most often in children. But they can develop at any age.

Food allergy symptoms can range from mild to severe (see Wise Choices box). Some people experience a life‐threatening reaction called anaphylaxis. Symptoms may include trouble breathing, dizziness, and fainting. When you have a food allergy, there’s no way to predict how your body will react when you’re exposed. You might have a mild reaction one time and a severe reaction the next.

If you think that you or your child may have a food allergy, see your health care provider. Your doctor will take a detailed medical history and perform a physical examination. If a diagnosis of food allergy seems likely, they may recommend a blood test or skin prick test. These results will help determine if you or your child has a food allergy.

NIH researchers have been working to better understand food allergies. “There has been a lot of research on peanut allergy because it is often severe, lifelong, and has a huge impact on quality of life,” explains Dr. Scott Sicherer, a pediatric food allergy expert at Mount Sinai’s Icahn School of Medicine. Scientists hope the progress they make on peanut allergy will help guide how to handle other food allergies.

Researchers recently carried out a large clinical trial called Learning Early About Peanut Allergy (LEAP). The study looked at infants’ chances of developing an allergy if they ate peanut-containing foods at an early age. Six hundred and forty infants who were at high risk of developing a peanut allergy were enrolled in the trial. The infants were randomly placed in either a peanut-eating or peanut-avoiding group. They continued these diets until they were 5 years old. Infants who ate peanut-containing foods beginning early in life had an 81% lower chance of developing a peanut allergy.

“Based on the strength of these findings, an expert panel sponsored by NIH recently issued updated guidelines to help health care providers work with families to introduce peanut-containing foods to infants to help prevent the development of peanut allergy,” Sicherer says.

The panel provided 3 guidelines that describe when and how to give these foods. The recommendations are based on how likely a baby is to develop peanut allergy. Talk with your doctor before you introduce any peanut-containing foods to your infant. The doctor may tell you when and how to start feeding peanut to your baby or recommend doing allergy testing first.

“It’s important to understand that these guidelines are about preventing peanut allergy, not treating an existing peanut allergy,” Sicherer explains.

The new guidelines may come as a surprise to some people. Almost 20 years ago, experts recommended that babies at high risk for developing peanut allergy avoid peanut-containing foods until age 3. But nearly 10 years ago, experts withdrew this recommendation. There was no proof that it worked.

“The most recent change in guidance was prompted by the very compelling results of the LEAP study,” says Dr. Marshall Plaut, a food allergy expert at NIH. “The new guidelines are based on these results and the clinical knowledge of the expert panel who developed them.”

Whether this strategy works for other food allergies isn’t known. “More research is needed to find out if early dietary introduction of other foods may help prevent allergy to those foods,” Sicherer explains.

NIH scientists are also looking at ways to treat people who already have food allergies. One promising strategy is called oral immunotherapy. It involves eating small, slowly increasing amounts of the allergy-causing food. One recent study tried this approach for peanut‐allergic preschool children. Almost 80% of children given the treatment could safely eat peanut-containing foods afterward. More studies are being done to improve the safety and effectiveness of the approach. The therapy is also being studied for people with milk and egg allergies in small clinical trials.

There may be other ways to provide this type of therapy. One ongoing study is investigating using a skin patch to deliver small amounts of peanut protein to peanut‐allergic patients. Early results have shown some promise among young children with peanut allergy.

Food allergy studies have to be done very carefully because reactions can be life threatening. “It’s important to understand how much careful thought goes into ethically designing research studies, particularly those involving vulnerable populations like children,” Plaut says. “Sometimes answers take longer than we would all like. But it’s critical to find them in a way and at a pace that is safe.”

For now, there are no treatments for food allergies. But avoiding allergy‐causing foods can help prevent symptoms. Read food labels carefully. Wash your hands and surfaces you touch to prevent accidental contact. Sometimes it can be difficult to avoid exposure completely. Carrying an epinephrine auto injector can be lifesaving. This device delivers a hormone that maintains blood pressure and can open your airways. Talk with your health care provider to learn more about preventing and treating food allergies.

Can spices cause allergic reactions?

The addition of spices and other additives to foods is extremely common. Spices are derived from plants and therefore have the potential to be allergens. They are often suspected as the trigger for allergic reactions, but allergic antibody mediated reactions are believed to be very rare. Most of the reactions patients have are not true allergic reactions (due to allergic antibody formation to the actual spice) and may represent non-allergic reactions consistent with “intolerances.” This is important to differentiate as true antibody mediated reactions can be life threatening, while a non-allergic reaction is likely to be self-limited (or in other words, ultimately resolving itself without treatment).

The following are types of reactions reported with spices:

Non-Allergic Reactions. Rash on the skin. Spices have properties that cause irritation on the skin and resulting rash. Example: Cinnamon can cause a local rash where it touches the skin.

Itching in the mouth. These types of reactions are often due to a cross reactivity with pollens. In essence, the allergy is not to the actual spice, but to the pollen, which can cause a localized itch in the mouth. Example: Reaction to fresh tarragon, but due to allergy to a type of weed.

Cough due to inhalation. This type of reaction is likely due to an irritant effect, rather than a true allergy. Example: Black pepper can cause cough or can trigger asthma symptoms in patients with asthma.

Allergic Reactions Anaphylaxis (severe allergic reaction). Although extremely rare, anaphylaxis has been reported with some spices. These reactions are consistent with true allergy. Case reports have described these types of reactions with oregano, thyme, coriander, caraway seed and cumin. There have also been rare reports of spices being adulterated with peanuts as filler, leading to previous FDA recalls of cumin, although no reactions in peanut allergic patients have been reported.

Sesame seed is a more traditional food allergen of growing concern and may be contained in spice mixtures. A reaction may be attributed to a true food allergy, and it can be life threatening. For patients known to be allergic to sesame, care should be taken in avoiding spices with sesame as an ingredient. The Food and Drug Administration is advancing a new effort for the consideration of labeling for sesame, in par with other major food allergens.

If a particular spice has been consistently causing symptoms, an allergist / immunologist should be consulted. In most cases, the reaction to a spice will be due to a non-allergic cause.