5 Answers About Adult-Onset Food Allergies

An overview of the common food allergies in adults, why food allergies require a professional diagnosis, and more.

A young adult is tested for food allergies using a skin prick test on the forearm.

Updated on May 21, 2024

An allergic reaction occurs when the body’s immune system overreacts to a substance that would normally be harmless. This reaction can involve symptoms like mild hives, itching, and congestion. It also has the potential to cause anaphylaxis, a life-threatening event where the airways close and the body goes into shock.

Food allergies are a type of allergy where the immune system overreacts to certain foods or substances in certain foods. Food allergies can begin at all different ages. Many people have food allergies during childhood. Many others experience their first symptoms as adults.

Here are five things to know about adult-onset food allergies.

The causes are not fully understood

The exact causes of food allergies are not fully understood. This includes why some people have food allergies and others do not, why some people outgrow their food allergies, and why some people develop allergies later in life. Food allergies are believed to be caused by a combination of genetic and environmental factors—a person’s genetics predispose them to having food allergies, and at a later point in their life, they are exposed to something that activates the allergies.

Food allergies require a diagnosis

While there are many adults living with food allergies, research has found that many people who report having food allergies have not received a professional diagnosis from a healthcare provider. If you have a history of food allergies but have not seen a healthcare provider—or it has been some time since you’ve seen a healthcare provider—make an appointment.

Certain food allergies are more common

As mentioned above, a person could develop an allergy to nearly any food, but most food allergies involve only a small number of foods—eggs, fish, milk, peanuts, shellfish, soy, sesame, tree nuts, and wheat. The most commonly reported adult-onset food allergies are shellfish, fin fish, peanuts, and tree nuts. However, adult-onset allergies can involve any food. People can also be allergic to multiple foods.

Oral allergy syndrome is also common

The most common type of food allergy among adults is oral allergy syndrome (OAS), also called pollen-food allergy syndrome (PFAS). It affects people who have pollen allergies, and is an allergy to uncooked fruits and vegetables, nuts, and spices. Consuming these foods can cause itching, swelling, redness, and discomfort in the eyes, ears, nose, and throat. Anaphylaxis is not common among people with OAS, but severe reactions can and do occur—and the possibility of this should be discussed with a healthcare provider.

Avoidance is the primary therapy

Food allergies cannot be cured, but the condition can be managed. The only proven method for avoiding allergic reactions is avoiding trigger foods. People will also need an emergency plan in place in case of a severe allergic reaction—including carrying epinephrine autoinjectors to treat anaphylaxis. People may also be advised to carry antihistamine medications to use in case of mild reactions.

Additionally, new therapies are becoming available. These include immunotherapies and biologic therapies that can be used in combination with avoiding trigger foods. These therapies can reduce the severity of a reaction to accidental exposures.

Because people with food allergies may need to avoid multiple foods, they may also have a more difficult time meeting their nutritional needs. Nutritional deficiencies can contribute to other health problems. This is another topic that should be discussed with a healthcare provider.

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