Why New Allergies Can Suddenly Appear In Adults As Immune Triggers Shift

Allergies are not limited to childhood. Experts say people can develop new allergies at any stage of life, sometimes after years without symptoms.

Researchers have identified several unexpected allergy triggers, including COVID-19, antibiotics, pregnancy, menopause and tick bites.

A 2026 study linked COVID-19 infection to a significantly higher risk of allergic rhinitis and asthma. Dermatologist Philip Curman said infection increased the risk, while vaccination reduced it.

COVID can intensify inflammation associated with allergic disease.

Respiratory syncytial virus and rhinovirus may produce similar effects, particularly in children. When the immune system is already fighting an infection, it may mistakenly treat harmless substances as threats.

Antibiotics may raise allergy risks by disturbing the gut microbiome, the community of bacteria that supports immune function.

Researchers believe this disruption can cause the immune system to misidentify harmless substances.

Hormonal changes can trigger allergy-like symptoms. About one-third of women with existing environmental allergies may experience worsening symptoms during pregnancy.

Pregnancy rhinitis can cause sneezing, congestion and a runny nose but usually disappears after childbirth. Hormonal shifts may contribute to new allergies after menopause.

Tick bites can trigger alpha-gal syndrome, a potentially serious allergy to red meat. More than 90,000 cases were diagnosed in the US between 2017 and 2022.

Sudden-onset allergies can become permanent. The immune system produces antibodies against substances it mistakenly identifies as harmful, causing symptoms ranging from itching and congestion to potentially life-threatening anaphylaxis.

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