A mild allergic reaction to shellfish may be treated at home. Hives or rashes can be treated with over-the-counter antihistamines, for example. People who have gastrointestinal problems after eating shellfish can usually take an over-the-counter stomach medicine, and some asthma symptoms may respond to inhalers. Most of the time, however, shellfish allergy symptoms are severe, and prompt medical attention may be required. Some people with severe shellfish allergies even carry an epinephrine injection.

A shellfish allergy occurs when a diner has an allergic sensitivity to the meat of marine animals with shells, including crab, lobster, and shrimp. It is often a serious and chronic medical condition. Instead of treating the symptoms of an allergic reaction to shellfish, most doctors recommend avoiding shellfish as much as possible. There may come a time, however, when a person with an allergy of this sort inadvertently consumes shellfish.

Hives are one of the most common signs of an allergic reaction to shellfish. These hives appear as a red rash, usually visible on most of the body. They are also usually very itchy, and they may be accompanied by swelling. In mild cases, topical and oral antihistamines will usually help relieve these symptoms.

An allergic reaction to shellfish may also result in gastrointestinal problems. A person with a shellfish allergy will sometimes feel nauseous, for example. Vomiting and diarrhea may also occur. As long as these symptoms are not severe, an over-the-counter stomach medicine can usually be used to relieve them. It is also important to drink plenty of clear liquids to prevent dehydration.

Asthma-like symptoms may also be present during an allergic reaction to shellfish. This is typically caused by a person's airways constricting slightly. Some people with mild allergies may be able to relieve these symptoms with an antihistamine inhaler.

Someone who experiences a severe allergic reaction to shellfish will generally need prompt medical attention. This is especially true if his throat is swelling, of if he is having serious trouble breathing. If a person's throat swells enough, his airways may constrict, making it nearly impossible to breathe. Without treatment, this will often be fatal.

Epinephrine, also known as adrenaline, is a hormone produced by the human body. When injected into the body during an allergic reaction to shellfish, it can help reverse some of the more dangerous symptoms, such as swelling. Patients with severe allergies are usually encouraged to carry at least a single dose of epinephrine with them at all times. The effects of this injection will usually last until a person is able to get to a hospital.