Confusion in the immune system': How allergies can develop later in life

Allergies don’t always begin in childhood. Allergists say new allergies can emerge at any point in life, sometimes long after someone has previously been symptom-free. The article describes multiple “triggers” that can turn on an immune response, including genetic predisposition paired with an environmental switch. It highlights infections as one pathway: a 2026 study finds that contracting COVID-19 is linked to a significantly higher risk of developing allergic rhinitis (hay fever) and asthma, while vaccination was associated with a lower risk. The piece also notes similar potential effects from RSV and rhinovirus in children. It further discusses how antibiotics may raise allergy risk by disrupting the gut microbiome, and how pregnancy can alter the immune system and lead to unexpected changes in existing allergies.