Allergies arise from the body's attempt to reject foreign substances. If you have a happy, healthily immune system it works to destroy invading germs and other foreign substances that might make you ill. When the immune system functions inappropriately, reacting to innocuous substances, we have allergies. For example, pollens, which we would best ignore, evoke a runny nose, tearful eyes and sneezing.

Hayfever, which can certainly ruin your day, itchy scaly allergic dermatitis, and asthma, with it's scary reduction in lung capacity, are three illnesses collectively known as "atopic diseases." These are the "hardwired" allergic responses, or "Type I Hypersensitivities". They involve the release of histamine, which in turn triggers inflammation - hence the use of antihistamines to block these allergic responses.

Another "hardwired" Type I reaction is "anaphylactic shock", where exposure to "allergen" triggers massive inflammation, which if untreated, can even kill you - touch peanut and die.

Dreadful as they are, however, these Type I diseases are just the tip of the iceberg. "Clinical Ecologists", a new non-conventional medical speciality dedicated to the research and treatment of allergies, work with two major allergic definitions: "fixed allergies" (the Type I) and "cyclical allergies".

Cyclical allergies are not, thankfully, hard wired. Where fixed allergies have been classified as the various "hypersensitivities", the cyclical allergies are more complex, usually not life-threatening, but nevertheless bedeviling, "sensitivities". The symptoms, and their degree of trouble, can come and go, and if you avoid the triggers you can develop a tolerance. This makes cyclical allergies hard to sort out. Each individual responds in a unique manner, and the immune system is a surprising, uncharted and complex system operating and interacting with many levels, not least, mental and emotional. If you have any of the most commonly reported symptoms of environmental sensitivity, such as an inability to concentrate, confusion, fatigue, headaches, digestive problems, skin problems, you may have cyclical allergies.

To get a mental picture of the process of developing a sensitivity, imagine opening your eyes in the dark, adjusting and adapting your vision to the darkness, and then not being able to readapt to the bright light. With allergies the body's immune system has become deregulated - it no longer adapts. Often the hypersensitivity may begin after a chemical exposure. The body has to cope with an emergency, and then becomes hypervigilent. Like a country at war obsessed with spies the hypervigilant immune system reacts to non pathogens; pollens, dust mites, molds, common foods and chemicals. Chemicals! Perhaps the thousands of synthetic chemicals we now exposed to are part of the evocation of hypersensitivity. Allergies are becoming more common. This rapid growth is well documented in the case of asthma.

Type I hypersensitivities can usually be diagnosed with sophisticated blood tests called RAST and ELISA, but if your allergies are cyclic, that's another matter. The skin scratch tests used by conventional allergist are only 30% reliable. You would be better off flipping a coin! The skin prick tests of the Clinical Ecologists are only a little better. More promising are the various divining techniques, which include electrodermal testing (such as the "Intero"), and simple "muscle testing". The proponents of these diagnostic methods claim they are probing the bodies energy patterns. As a scientist, all I can tell you about these techniques is that they are divining systems. If you were looking to dig a well you'd best use a water diviner. Likewise, if you are looking for allergies a divining system, in talented hands, may be the best short cut.

The only "reliable" way of sorting through sensitivities is through avoidance and challenge. Avoidance: often the body's responses to provoking stimuli are exhausted, so, for example, if you wish to test for sensitivities to food you should avoid all suspect foods for four days to "unmask" the sensitivity.

There are several treatment options. One important aspect in dealing with the problem is to try to avoid exposure to the potential triggers. You will want to avoid cigarette smoke, and solvents, and fragrances, and dust, molds, etc. While not always possible in practice, avoidance is an important part of any rational treatment for we must try to minimise the "insult" to the system. Diet is one area where we can control what we are exposed to. Diet therefore become very important.

Because it is the foods that we are most exposed to that we develop reactions to, it is very common for wheat and dairy to be culprits. We can look at our intestines as our main (chemical) interface with the world. In hypersensitivity there is almost always a problem with digestion. We often see a "leaky gut" syndrome. In a healthy gut perhaps 2% of protein is absorbed as peptides, and the rest as amino acids. In the stressed intestine up to 20% of protein may be absorbed as peptides to which sensitivities can develop. So a "leaky gut" sets up a vicious circle of sensitivities. Often a carefully planned "rotation diet" will break this cycle of illness.

My role as the doctor is to help the patient through the jungle of possible causes and probable answers. As well as sorting out what you are reacting to, we can use herbs to heal the gut and the immune system, and homeopathy to heal and re-tune the body.

An important part of a holistic approach to allergies is detoxification. When we stop taking in toxins, we start to excrete them. To understand this, consider the body's reaction to cigarettes. The first cigarette is rejected with total energy: you might cough, vomit, turn green and cry. But the smoker would die of exhaustion if the body continued such resistance. So we surrender. Later, if you give up smoking you will redevelop your sensitivity to smoke. The same is true with foods, so we see an apparent paradox. If you eat junk, you will tolerate junk. As you eat well and the body recovers its purity and its strength, so you will become sensitive to crap, and this is a very healthy response.