Adult-Onset Allergies: Why New Allergies Can Start Later in Life

Yes, you can develop allergies as an adult, even to things that never bothered you before. The American Academy of Allergy, Asthma and Immunology (AAAAI) says allergies can develop at any time and affect people of all ages, and that about 20% of people with hay fever first get symptoms after age 20.

Some types are more likely than others to start in adulthood, including hay fever, medicine allergies, some food allergies and a red meat allergy linked to tick bites. This guide explains which allergies show up later, why it happens and what to do. For more, see our living with allergies guides.

Jump to: Quick answer · Which allergies start in adults · Why it happens · Symptoms · What to do · FAQ

Quick answer

• It’s common: AAAAI says it is not uncommon to develop allergies as an adult.
• Hay fever: about 20% of people with hay fever develop symptoms after age 20, and symptoms often peak in the 20s and 30s (AAAAI).
• Medicine allergies: the most common age for a new medication allergy is 20 to 49 (AAAAI).
• Food: in a large U.S. survey, 48% of adults with a food allergy reported developing food allergies as an adult. Shellfish was the most common food allergy in adults.
• Red meat after a tick bite: alpha-gal syndrome is mostly reported in adults; the CDC says as many as 450,000 people may be affected in the U.S.
• Get tested: an allergist can find out what you are reacting to.

Which allergies tend to start in adulthood?

Food allergies in adults

A 2019 survey of more than 40,000 U.S. adults, published in JAMA Network Open, estimated that 10.8% have a convincing food allergy. The most common were shellfish (2.9%), milk (1.9%), peanut (1.8%), tree nuts (1.2%) and fin fish (0.9%). Nearly half (48%) of adults with a food allergy reported developing food allergies as an adult, and 51% had had a severe reaction.

The American College of Allergy, Asthma and Immunology (ACAAI) notes that food allergies are more common in young children, but says it is truly possible to develop one as an adult. If you have an immediate reaction to a food, ACAAI advises seeing a board-certified allergist for testing. Food allergies usually cause an immediate, repeatable reaction, unlike food intolerances, which tend to cause vaguer, delayed symptoms. Our food allergy guides cover daily life with one.

Red meat allergy after a tick bite

The CDC describes alpha-gal syndrome as a serious, potentially life-threatening allergy to alpha-gal, a molecule found in most mammals but not in people. In the U.S., it is mainly linked to bites from the lone star tick. More than 110,000 suspected cases were identified between 2010 and 2022, and the CDC says as many as 450,000 people may be affected. Most healthcare providers advise avoiding red meat such as beef, pork, lamb and venison, and some people also need to avoid dairy and certain medicines or other mammal-derived products.

Why do adults develop new allergies?

No one is born with allergies; they develop after the immune system meets a substance and starts treating it as a threat. Experts point to a few reasons this can happen later in life:

• An aging immune system. On ACAAI’s patient site, allergist Jonathan Olsen, MD, explains that as the body ages, the immune system ages too, and it may start treating something harmless, like tree pollen, as a threat.
• New exposures. Dr. Olsen gives examples: moving to a new environment, getting a new pet, or changing jobs.
• Repeated exposure. AAAAI notes that medicine allergies can develop after repeated exposures over years.
• Genes and life events. AAAAI says genetics play a role, and that stress, infection and changes in the environment can alter the immune system over time.

Symptoms to watch for

Adult allergy symptoms are the same as in children. They depend on the trigger:

• Nose and eyes (pollen, dust mites, pets, mold): sneezing, a runny or stuffy nose, itchy or watery eyes. These can be mistaken for a cold that never ends.
• Skin: hives, itching or a rash. See our guide on telling dry skin from an allergic rash.
• Food or medicine: hives, swelling, vomiting, or trouble breathing soon after a food or dose. With alpha-gal syndrome, the CDC notes symptoms can range from mild to severe.

Call 911 or your local emergency number for trouble breathing, swelling of the throat or tongue, or feeling faint after eating, taking a medicine or being stung.

What to do if you think you have a new allergy

1. Write down what happens. Note when symptoms start, where you are, and what you ate, took or touched.
2. See an allergist. ACAAI’s advice is simple: an allergist can test you and find out what you are allergic to. AAAAI recommends that medicine allergies always be evaluated by a board-certified allergist.
3. Don’t assume an old allergy is still there, either. AAAAI notes that people often lose medicine allergies with time, which an allergist can check.
4. Reduce exposure once you know your trigger. For pollen, see our pollen avoidance guide; for dust mites, see how common dust mite allergy is and what helps; for animals, see our pet allergy guides.
5. Ask about treatment. Medicines can control symptoms, and allergy shots or tablets can help some people with pollen or dust mite allergies over the long term.

This guide is general information, not medical advice. Read our medical disclaimer.

Frequently asked questions

Can you develop allergies as an adult?

Yes. AAAAI says allergies can develop at any time and affect people of all ages. Hay fever, medicine allergies, some food allergies and alpha-gal syndrome often start in adulthood.

Why did I suddenly develop allergies?

Possible reasons include an aging immune system, a new home, pet or job, and repeated exposure to a medicine. Genes, stress and infections can also play a role. An allergist can test for the cause.

What is the most common food allergy that starts in adults?

Shellfish is the most common food allergy in U.S. adults, at 2.9% in a 2019 national survey, followed by milk, peanut, tree nuts and fin fish.

Can you suddenly become allergic to red meat?

Yes. Alpha-gal syndrome is an allergy to red meat and other mammal products linked mainly to lone star tick bites in the U.S. The CDC says most reported cases are in adults.

At what age do adult allergies usually start?

It varies by type. AAAAI says hay fever symptoms often peak in the 20s and 30s, and new medicine allergies most often start between 20 and 49. Food and alpha-gal allergies can start at any adult age.

Can adult-onset allergies go away?

Some can. AAAAI notes that people often lose medicine allergies over time. Others, like many food allergies, tend to last, so check with an allergist before trying a food or medicine you reacted to.

Sources

• American Academy of Allergy, Asthma and Immunology. Developing allergies. June 18, 2026.
• American College of Allergy, Asthma and Immunology. Can allergies develop later in life? August 14, 2026.
• American College of Allergy, Asthma and Immunology. Is it possible for adults to get food allergies? July 11, 2025.
• Gupta RS, Warren CM, Smith BM, et al. Prevalence and severity of food allergies among US adults. JAMA Netw Open. 2019;2(1):e185630.
• Centers for Disease Control and Prevention. About alpha-gal syndrome. Reviewed January 5, 2026.

Last reviewed: October 21, 2026.