A rise in allergies has turned the sale of specialist wheat-free and dairy-free products into a multi-million pound business.

The market researchers Mintel say the value of "free-from" foods aimed at consumers on special diets has more than quadrupled in the past five years to £90m.

Rising numbers of people are diagnosed as having gluten, wheat or nut intolerance while there are more vegans whose diet excludes dairy products. Many supermarkets devote aisles to the sale of free-from foods such as soya milk, wheat-free breads and even gluten-free ale.

Mintel's report, published today, reports a rise of 327 per cent in sales of free-from products between 2000 and 2005 and predicted sales will double again by the end of the decade. Some 170 foods can spark allergies but eight foods account for the majority - cow's milk, eggs, fish, peanuts, other nuts, soya, shellfish, wheat and other cereals.

Julia Sloan, Mintel's consumer analyst, said that free-from diets were also fast becoming a "trendy lifestyle choice". Celebrities including Carol Vorderman, Geri Halliwell and Victoria Beckham are reported to follow wheat-free and dairy-free diets.

Mintel's survey shows that gluten and wheat-free products recorded particularly strong sales, rising by almost 120 per cent over the past three years to £48m. Dairy-free products were valued at £32m, growing by 28 per cent over three years.

As well as supermarkets, a number of niche suppliers are thriving in the free-from market. Anna Rowland and her partner, Jeff Willis, set up the website wheatanddairyfree.com a year ago, stocking 400 wheat- and gluten-free products. Ms Rowland, from Lewes, Sussex, had to start a gluten and wheat-free diet 10 years ago after a gastro-illness. She said: "Ten years ago there wasn't anything and I just remember how difficult it was."