Shellfish are classified as aquatic invertebrates and divided into two primary groups: mollusks which include scallops, clams and oysters, and crustaceans that include shrimp, crab and lobster. An allergic reaction to red shellfish is typically seen in adolescents and adults, with 60 percent of people first experiencing an allergic reaction in adulthood. This reaction begins within minutes to a few hours of ingesting the food, and the severity of the symptoms may vary among individuals.
Red Shellfish
Astaxanthin is a red carotenoid, and the source of the red or pink pigment in shellfish such as lobster, crabs and shrimp. Astaxanthin is a powerful antioxidant with numerous biological functions. In humans, this carotenoid protects our cells, tissues and neurons from oxidative damage due to free radicals. Oxidative stress has been shown to cause different forms of cancer and neurodegenerative diseases including Alzheimer's disease. This carotenoid also prevents the peroxidation of lipids in cellular and mitochondrial membranes by free radicals and inhibits the oxidation of low-density cholesterol, which, if left unchecked, results in the formation of arterial plaque. It also improves by our immune system by stimulating an increase in the production of antibody producing cells.
Immune Response to Shellfish
An allergic reaction to shellfish occurs when the immune system identifies certain proteins or the astaxanthin in shellfish as foreign and harmful. The immune system activates and releases pro-inflammatory immune cells that attack and destroy these proteins. These inflammatory immune cells also release histamine and other chemicals into the bloodstream and skin. Histamine and the pro-inflammatory cells such as basophils and mast cells are responsible for the symptoms of an allergic reaction to red shellfish. An individual who develops an allergic reaction to one group of shellfish is more likely to be allergic to other types of shellfish in that group.
Symptoms of an Allergic Reaction to Red Shellfish
The classic symptoms of an allergic reaction to shellfish include an itchy, red rash known as hives that develops within minutes of ingesting shellfish. The release of histamine increases the permeability of blood vessels resulting in the swelling of the face, lips and tongue. Angioedema, or swelling of the deeper layers of skin, and throat swelling, difficulty breathing, wheezing and nasal congestion are also observed. A severe allergic reaction to red shellfish can lead to a life-threatening condition known as anaphylaxis. Its symptoms include nausea, abdominal pain, vomiting, dizziness, constriction or closing of the upper respiratory tract, increased heart rate and loss of consciousness. If you experience a swollen throat or any symptoms indicative of anaphylactic shock, seek immediate medical attention.
Treatment of an Allergic Reaction to Red Shellfish
If you experience a mild allergic reaction to red shellfish, over-the-counter corticosteroids such as hydrocortisone and antihistamines will reduce the inflammation and associated symptoms including itching and hives. If you experience a severe allergic reaction to red shellfish, seek immediate medical attention to receive an epinephrine injection. Some physicians recommend carrying an epinephrine autoinjector since it is quite possible for an individual to unintentional purchase seafood fried in the same oil as shellfish.
References
- Southwest Allergy & Asthma Center; "Shellfish Allergy"
- Food Allergy & Anaphylaxis Network; "Shellfish Allergy"
- Beta Force; "Astaxanthin - Frequently Asked Questions"
- MayoClinic.com; "Shellfish Allergy"; June 2011
- Cleveland Clinic; "Shellfish Allergies"
- Auckland Allergy Clinic; "Seafood Allergy"; February 2003
