Allergy: Symptoms & Signs

Medically Reviewed on 9/10/2019

Allergies are exaggerated immune responses to environmental triggers known as allergens. Allergies are very common, and about 50 million people in North America suffer from allergies. One of the most common forms of allergy is allergic rhinitis ("hay fever"), which produces symptoms like

The symptoms of hay fever can, in turn, lead to fatigue and lethargy. Other types of allergic reactions can involve the skin (hives and itching). Anaphylactic shock is a severe form of allergic reaction that can be life-threatening. In anaphylactic shock, there is swelling of the throat and difficulty breathing. Asthma is also related to allergies in many cases.

The symptoms of allergies can sometimes resemble those of other conditions. The common cold and the flu can cause respiratory symptoms similar to allergies. Typically, allergy symptoms are associated with a specific time of year or exposure to an allergen.

Causes of allergies

Allergies result from an inappropriate or misguided reaction to foreign substances (usually harmless substances). Allergens are the substances that trigger allergies. Pollens are the allergens that cause hay fever, one of the most common types of allergic reaction.

Summary of Common Allergy Symptoms by MedicineNet Staff
A review of our Patient Comments indicated that many people with allergies have similar symptoms and signs. Oftentimes, an allergy attack began with itchy eyes followed by facial swelling, particularly of the eyes and lips. Some patients mentioned that the itchiness occurred all over their bodies, and sometimes they developed hives. Several people indicated that their symptoms felt flu-like, in that they experienced coughing, fatigue, and the sensation that they had a fever. Read on to learn more about allergy symptoms in our Patient Comments.

Related Symptoms & Signs

Other allergy

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References Allergy Types.