Allergy symptoms can be categorized as mild, moderate, or severe.

Mild Allergic Reactions

Mild allergic reactions can include:

Rash or hives
Itchy, watery eyes
Congestion
Mild reactions do not spread to other parts of the body.

Moderate Allergic Reactions

Moderate reactions can include symptoms that spread to other parts of the body, including:

Itchiness
Difficulty breathing
Severe Allergic Reaction (Anaphylaxis)

Anaphylaxis is a rare, life-threatening emergency in which the body's response to the allergen is sudden and affects the whole body. It may begin with sudden itching of the eyes or face and within minutes progress to more serious symptoms, including:

Varying degrees of swellings that can make breathing and swallowing difficult
Abdominal pain
Cramps
Vomiting
Diarrhea
Mental confusion or dizziness

Reviewed by the doctors at The Cleveland Clinic Department of Pulmonary, Allergy and Critical Care Medicine.

Edited by Charlotte E. Grayson, MD, Feb. 2004, WebMD.

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