A study published in the July 2004 Journal of Allergy & Clinical Immunology shows that seafood allergies are much more prevalent than once thought, with more than 6.5 million Americans believed to be affected. The study "Prevalence of Seafood Allergy in the U.S." revealed that the onset of seafood allergy is likely to begin in adulthood, and frequent, severe reactions are reported by sufferers.

In all, about 11 million people -- roughly 1 in 25 Americans -- are believed to be affected by one or more food allergies, a disease triggered by the ingestion of certain foods that may cause life-threatening reactions, or anaphylaxis, according to The Food Allergy & Anaphylaxis Network (FAAN), a co-investigator of the nationwide survey.

Seafood, common in the U.S. diet, includes fish (cod, salmon and tuna, for example), and shellfish (shrimp, crab and lobster, squid, scallop, clams, mussels and snails). The study showed that a shellfish allergy is reported by 1 in 50 Americans and a fish allergy by 1 in 250.

The reported rate of onset was during adulthood for approximately 60% with shellfish allergies and 40% with fish allergies. In all age groups, adults reported a prevalence of at least 2.5%, while among children the highest prevalence reported was 0.8% in the 6-17 age group.

Among adults, women reported more allergies than men, and among children, boys were affected more often than girls. The highest rate (3.7%) of seafood allergies was reported by African-Americans.

"Further studies are needed to determine the reason for women and minorities having a higher rate of seafood allergy, whether it is cultural eating differences, associations with environment exposures or other explanations," said Dr. Scott Sicherer, co-author on the study.

"What we do know is that seafood-allergic reactions may be potentially life threatening and should be taken very seriously, yet many of the participants did not seek proper diagnosis and treatment. We need to get the word out so that sufferers get an appropriate diagnosis and can learn how to prevent and treat reactions to ensure their safety."

Seafood consumption of both finfish and shellfish has increased by 25% since 1970. More specifically, the seafood consumption rate has risen from a per capita consumption of 12.5 pounds in 1970 to 15.6 pounds in 2002. (Source: http://www.publicaffairs.noaa.gov/releases2003/sep03/noaa03105.html, accessed December 2003.)

A high number of recurrent and severe reactions were reported in the study. Multiple reactions were reported by 53% for fish and 57% for shellfish. In 55% of fish reactions and 40% of shellfish reactions, evaluation by a physician or care in an emergency room was sought. Treatment of severe symptoms and administration of epinephrine, the drug of choice for treating a severe allergic reaction, was reported in only 15% of seafood-allergic patients.

"FAAN has launched a Seafood Allergy Registry to learn more about this national healthcare issue. We encourage anyone with a seafood allergy to participate," said Anne Munoz-Furlong, CEO and founder of FAAN, a patient advocacy group. "We are hopeful that through the Seafood Allergy Registry we can learn much more about why allergic reactions begin in adulthood, why the reactions are so severe as well as how to avoid such severe reactions. The findings will not only help seafood allergic individuals, but the seafood and food industry, especially in the areas of food labeling and product development."