This is a controversial area and one which tends to attract a lot of media attention. Basically, though, there are several effects on the CNS which can be linked to food allergy:
1. Migraine
The tendency to suffer from this severe form of headache runs in families. The headache is often proceeded by an 'aura' such as visual hallucinations in the form of flashing lights. Generally, only one side of the head is affected and the pain is usually accompanied by nausea. In most cases the migraine continues for 8-24 hours; sufferers often find it impossible to function normally while it lasts. In recent times the long-held belief that certain foods such as chocolate, wines, yeast extracts, hard cheeses, milk and eggs are linked to migraine headaches, has been proved beyond doubt and several offending compounds have been identified.
2. The Allergic Tension-Fatigue Syndrome
Many allergic children have pale faces with dark rings under their eyes, giving them a tired look. They may be difficult to rouse in the mornings and tend to concentrate poorly at school, also especially in the mornings. A large number are rather irritable in general and may be unable to fall asleep easily at night. It has been found that there is a link between this syndrome and an excessive intake of milk, cola drinks and chocolate. Cutting these problem-causers out of their diet can improve the behaviour of these children quite dramatically.
3. Hyperactivity
Dr Ben Feingold, an American allergist, has become well-known for drawing attention to the apparent connection between behaviourial problems and the presence of food additives in the diet. The story of how he reached his conclusion is a long one, but inessence depended on his observations that some adult patients reacted adversely to aspirin. He felt that in addition to causing their asthma, aspirin also appeared to change the patients' behaviour, making them more restless.
If this was so, he reasoned, then the effects in children diagnosed as hyperactive might be even more striking. Hyperactive children typically rush about in purposeless and often destructive activity, often putting their parents under considerable strain. It was thought that one solution might be to remove salicylic acid (used in aspirin) and its derivatives from their diet. (Several foods also contain natural salicylates.In Dr Feingold's view, these preservatives served no essential purpose and would not be missed if children ate foods that were free of them. He then went even further. The yellow food dye, tartrazine, has a similar effect to aspirin in some sensitive asthmatics, so he suggested that it might play a similar role in hyperactivity. From there it was only a short step to the elimination of all artificial colouring and flavours from the food of hyperactive children. Considerable success has been claimed in using this diet (known as the Feingold Diet) in the management of these children.
Unfortunately, however, no properly controlled study has been able to confirm this theory, which has resulted in much controversy in many countries.