The Delayed Food Allergy Syndrome (DFAS) is a valid and useful concept which unifies into one diagnosis symptoms so diverse and nonspecific that they are seldom thought of as a unit or as allergic. This condition occurs most frequently in childhood, but can also occur in teens and adults. Many physicians, and even some allergists, are unaware of the Delayed Food Allergy Syndrome or are doubtful of its validity. In spite of the fact that there is little data from medical research about this condition, it has gained its greatest acceptance amongst allergists who care for children.
DFAS can manifest itself in many different ways and in many organ systems. The seven most common signs and symptoms in approximate order of frequency are:
Like most syndromes, the Delayed Food Allergy Syndrome often occurs in incomplete or partial forms. Only rarely are all seven of the major signs and symptoms present. One can, however, expect three to four of them to become evident in the medical history, if one inquires carefully.
While respiratory tract allergy and fatigability may be more or less constant, the other complaints are likely to be intermittent. Headache and stomachache for example, can be assumed to occur sooner or later in almost everyone, but it is their greater than expected frequency that may be significant. Individually, each of the above symptoms may be due to many different causes. When they present in combination, however, the possibility of the DFAS should be considered.
Less frequent symptoms which have been described with the Delayed Food Allergy Syndrome include cervical gland enlargement, constipation, loose stools or diarrhea, impaired hearing, bed wetting, and mildly elevated temperature.
This syndrome is usually thought to be due to a food allergy. By far, the food most commonly responsible for this delayed allergy is milk. Both parents and physicians find it difficult to believe that foods eaten almost daily, such as milk, wheat, corn, or chocolate can be responsible for the occurrence of such seemingly unlikely symptoms. Particularly difficult to understand is the tendencies for the Allergy Tension Fatigue Syndrome to become more evident in the winter, and in some cases to almost disappear in summer despite no significant change in diet.
At the present time there is no readily available test which can reliably identify the allergens responsible for the delayed onset type of food allergy responsible for DAFS. Allergy skin testing or RAST or ImmunoCap blood tests are not helpful, as they measure only the IgE antibody, the antibody responsible for immediate allergic reactions. Research has not yet identified the antibody or antibodies responsible for delayed reactions, although there has been considerable interest and research in the possible role of the IgG antibody in the delayed allergic reaction. There is now a blood test available to measure this antibody, but its reliability as a predictor of delayed allergy has not yet been established.
The diagnosis of this type of food allergy is made by initiating an elimination diet and observing a decrease or elimination of symptoms. It is often recommended that the suspected food be totally eliminated from the diet for four week. If there is a significant improvement in symptoms, the physician may recommend that the food be reintroduced into the diet in order to see if the symptoms recur. If so, the food is once again eliminated. The elimination diet and challenge, therefore, if properly carried out, is the most reliable diagnostic tool in making the diagnosis.
If and when a food is identified as the causative agent, the food should be totally eliminated from the diet. In less severe cases, it may not be necessary for the food to be totally eliminated from the diet on a long term basis. Many food allergic patients with DFAS can tolerate minimal amounts of the allergens without developing symptoms. Exceeding one’s threshold of tolerance will, however, precipitate symptoms.
In summary, the Delayed Food Allergy Syndrome presents with a constellation of symptoms which, when appearing together, suggest to the allergist the possibility of a delayed onset food allergy, especially to milk. It is more common than is generally appreciated. It may accompany inhalant allergy, and explain inadequate response to the treatment of inhalant allergies such as a poor response to immunotherapy.
As a final note, it should be mentioned that food allergy is usually familial. The knowledge may greatly aid its recognition in a particular patient as well as other members of the family.