Allergies occur when the immune system reacts to a substance that is usually harmless to most people. Depending on the trigger and the person, the reaction can cause symptoms ranging from sneezing and congestion to skin reactions, breathing problems and, in some cases, life-threatening anaphylaxis.
Identifying the trigger can help guide treatment. Health professionals usually begin with a medical history and physical examination and may use skin or blood tests when needed. Allergy tests are not interpreted on their own, because a positive result can indicate sensitivity without necessarily proving that a substance is causing a person’s symptoms.
Among the common allergy triggers are pollen, mold, animal allergens, natural rubber latex and certain foods.
Pollen
Pollen from trees, grasses and weeds is a common cause of allergic rhinitis, often called hay fever. Symptoms can include sneezing, a runny or blocked nose, and itchy or watery eyes.
The timing and severity of symptoms depend on the plants involved and local conditions. Once a specific pollen allergy has been identified, treatment can include reducing exposure to the trigger and using medicines recommended by a health professional. Allergy testing can help identify the substances responsible for symptoms.
Mold
Mold grows in damp environments and can release particles into the air. Exposure can cause respiratory symptoms in some people and can worsen asthma. CDC guidance recommends addressing the moisture that allows mold to grow, including fixing leaks and keeping indoor humidity low.
CDC recommends keeping indoor humidity no higher than 50% where possible and drying wet areas within 24 to 48 hours to limit mold growth. People with allergies, asthma or certain other health conditions can be more sensitive to mold exposure and may need to take extra precautions during cleanup.
Animal allergens
Pet allergies are caused by proteins found in an animal’s skin flakes, saliva and urine, rather than by fur itself. These allergens can become attached to hair and spread through the home.
Symptoms may include sneezing, nasal congestion and other respiratory problems. Mayo Clinic recommends reducing exposure to the animal allergens. For people who keep a pet, measures such as keeping the animal out of the bedroom, regular bathing and grooming, and using high-efficiency particulate air filters may help reduce exposure.
Latex
Latex allergy is a reaction to proteins in natural rubber latex. The material is used in some medical products and other items, although synthetic alternatives are available.
Reactions can include skin irritation and rashes, while severe reactions can include anaphylaxis. The FDA advises people with a natural rubber latex allergy to use medical gloves made from alternative synthetic materials such as nitrile, polyurethane or PVC.
People who suspect they have a latex allergy should tell health professionals before medical procedures so that appropriate products can be selected.
Food
Food allergies occur when the immune system reacts to a protein in a particular food. Reactions can affect the skin, digestive system, respiratory system or cardiovascular system and can range from mild symptoms to potentially life-threatening anaphylaxis.
The foods that need to be avoided vary by person and country. WHO and the FAO maintain international work on priority food allergens and risk assessment, reflecting differences in the foods and allergen exposures that require attention.
For people with a confirmed food allergy, avoiding the responsible food is a key part of prevention. People at risk of severe reactions may also be prescribed epinephrine, also known as adrenaline, for emergency treatment. Anaphylaxis requires urgent medical attention.
Managing allergies
There is no single approach that works for every allergy. Treatment depends on the trigger, the severity of symptoms and the individual’s medical history.
A health professional may recommend avoiding the allergen, medicines to control symptoms or, for some allergies, allergen immunotherapy. Proper diagnosis is important because allergy tests can sometimes produce false-positive or false-negative results and need to be considered alongside a person’s symptoms and medical history.
Some childhood food allergies can resolve as a child grows, while others can persist into adulthood. Whether an allergy changes over time depends on the specific allergy and the individual, so claims that allergies generally disappear or always remain lifelong should be treated cautiously.
For people who experience recurring or unexplained symptoms, medical evaluation can help determine whether an allergy is responsible and identify appropriate ways to manage it.
