Could you be killed by a kiss? For those with severe food allergy – the ‘exquisitely sensitive’ as doctors call them – a microscopic amount of the food is enough to provoke a severe reaction. A smear of the food left in a badly washed cooking pot can do it, or a trace left on a work-surface. And the killer-kiss has nearly occurred on at least two occasions. A young man with fish allergy kissed his girlfriend shortly after she had eaten fried mackerel, and had to give emergency treatment for the consequences. In another incident, a young boy was kissed affectionately by his aunt, who had just consumed a packet of peanuts. She had forgotten about his peanut allergy, and was horrified to see, within a few moments, his lips and face swelling with the allergic reaction.
The allergens mentioned above does not represent all food allergens, but the most well known food allergens.
Both these reactions were extreme (and unusual) examples of IgE-mediated food allergy, one of the classical allergic diseases. This kind of response usually occurs immediately after eating the food and first affects the lips, tongue and mouth, and often the throat. Much less commonly, it can occur some hours later, and affect the stomach and intestines. In babies with food allergy, a delayed reaction that manifests as stomach pain, vomiting, and diarrhoea is actually more common.
In the mildest form, IgE-mediated food allergy produces a tingling or itching of the mouth, sometimes, with slight swelling of the lips, mouth and face. More severe reactions cause a dramatic swelling of the lips, tongue and throat. Both are described as local reactions because only the areas that contacted the food are affected.
When the swelling in the month is severe, there are often symptoms in more distant parts of the body as well, caused by food allergies that have entered the bloodstream. This is described as a systemic reaction because the body-system as a whole is affected.
The name used for systemic allergic reactions is anaphylaxis and, where it is severe enough to cause collapse, anaphylactic shock. It is important to be familiar with the symptoms of this because it can kill remarkably quickly. Recognising the problem at an early stage, and taking the right sort of action, can prevent a death.
Anaphylactic shock is the most frightening of all sensitivity reactions to food. Because it is potentially fatal, many sufferers, or their parents, must live in a state of perpetual vigilance to avoid eating the food by accident.
This is particularly difficult when extremely small amounts of the food provoke a full-blown anaphylactic reaction. Fortunately, the proportion of allergy sufferers who develop severe food allergies of this kind is relatively small.
One of the reasons that doctors dislike the use of ‘food allergy’ as a loose term for food intolerance is that true IgE- mediated food allergy can be such a dangerous disease. Those affected by true food allergy need to be taken seriously (by canteen staff or waiters, for example), and it does not help if thousands of other people also claim to have ‘food allergy’ on the basis of reactions such as headaches pr diarrhoea, which are certainly, debilitating but not life-threatening.
Most food allergies begin during childhood, but there are also cases of adults suddenly developing an allergy to a food, such as cow’s milk or sesame seeds, that had previously been eaten without trouble. No one can react to a food the first time it is encountered; there has to be an initial contact to sensitise the immune system. But this initial contact can, very rarely, occur before birth (from food molecules reaching the foetus in the mothers’s blood), or during breast-feading (from food molecules in the mother’s milk) so a child can react to a food the first time he or she eats it. New evidence suggests that peanuts allergens on the skin (e.g. from peanut oil in cream for nappy rash) are capable of sensitising children.