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This information was reviewed and approved by Carah Santos, MD (12/5/2022).

The severity and kinds of allergy symptoms depend on a person's genetics, the allergic condition and the type and amount of allergens involved.

There are many different types of allergic conditions. An allergic condition is the appearance of allergy signs and symptoms in specific organs or areas of the body. The most common allergy symptoms affect the nose, sinuses, lungs and eyes. However, in some conditions, organs such as the skin, digestive system and blood vessels can be affected as well.

Not all allergic reactions happen the same way. Some allergy symptoms occur immediately after exposure to an allergen, while others take hours or days to occur. Scientists think that the biological events leading up to immediate allergic reactions are different from those that result in delayed allergic reactions.

Immediate Allergic Reactions

Immediate allergic reactions typically occur within minutes of exposure to an allergen. Allergic reaction time will vary depending on a person's genetics and on the site of the body affected.

Delayed or Late-Phase Allergic Reactions

Delayed or late-phase allergic reactions generally occur 2 – 6 hours after exposure (and even longer in some people). Signs and symptoms of delayed or late-phase allergic reactions are generally the same as those for immediate allergic reactions.

In the case of allergic asthma, a delayed allergic reaction can cause other problems, such as loss of sleep due to nighttime asthma attacks. There are ways to time allergy and asthma medications to reduce symptoms of a delayed allergic response.

Symptoms of Specific Allergies

Learn about signs and symptoms of different allergens and allergic conditions:

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