* Allergies. Asthma-causing allergens/irritants include air pollution, tobacco smoke, pet dander, dustmites, pollen, cleaning products, kerosene heaters, moulds and mildew. Bakers, manicurists, hairdressers and painters, and those in the construction, auto-body, food-processing and petroleum industries often develop occupational asthma from breathing chemical and food vapours, flour and dust. Asthmatics are often allergic to common foods such as citrus, dairy, eggs, soya, wheat and yeasts (Am J Clin Nutr, 1997; 66: 526S-9S).

* Breastfeeding. Early exposure to cow’s milk often leads to allergy (BMJ, 1999; 319: 815-9), but at least three months of exclusive breastfeeding can decrease the rate of childhood asthma by at least 30 per cent. In children with a family history of allergy, rates may drop by as much as 50 per cent (J Pediatr, 2001; 139: 261-6).

* Probiotics. Lactobacillus given to mothers prenatally, and to their infants postnatally, for six months reduced the rate of atopic eczema in the children by 50 per cent at age two years (Lancet, 2001; 357: 1076-9). Nutritionists believe it will similarly benefit asthma sufferers.

* Stomach acid. Low levels of stomach acid can lead to a ‘leaky gut’, where undigested food particles pass into the bloodstream in the colon, increasing the likelihood of an allergic reaction. Have your stomach acid levels checked by a reputable physician or lab.

* Essential fatty acids. Fish, evening primrose and borage oil supplementation may reduce allergies (Med Hypoth, 2000; 54: 72-4). And new oils are being added to the list of ‘good’ fats all the time, like perilla seed oil, which may improve lung function in some asthmatics (Int Arch Allergy Immunol, 2000; 122: 137-42). New Zealand green-lipped mussel (Perna canaliculus) extract has also been found to be effective (Eur Respir J, 2002; 20: 596-600).

* Choose your fats carefully. High intake of trans fatty acids, found in milk, meats and margarine, may worsen allergy-related symptoms (Lancet, 1999; 353: 2040-1). Similarly, in a diet already high in omega-6 fatty acids, flaxseed oil (having both omega-6 and -3) may also worsen the balance of omega-6 to omega-3 in the body. Too much polyunsaturated fats (rich in omega-6) have also been implicated in increased rates of asthma (Thorax, 2001; 56: 589-95).

* Learn to breathe. Dysfunctional breathing may contribute to asthma attacks (BMJ, 2001; 322: 1098-100). The Buteyko method of correct breathing may help some sufferers (J Asthma, 2000; 37: 557-64). Yoga breathing exercises may also reduce attacks (J Asthma, 1991; 28: 437-42).

* An ioniser. Some studies report temporary relief from symptoms with ionisers (Paediatrics, 1966; 38: 405) while others have found no effects whatsoever (Thorax, 1983; 38: 919-22).

* Coffee. For men and women, regardless of age or smoking habits, just a single cup of coffee a day reduces asthmatic symptoms (Chest, 1988; 94: 386-9). This is because caffeine breaks down into theophylline, a bronchodilator widely prescribed for treating asthma. One - but no more than three - cups of coffee daily is sufficient.

* De-stress. Asthma can be worsened by stress, particularly in children (Lancet, 2000; 356: 982-7). Do what you can to reduce stress at home and elsewhere; yoga meditation can reduce airway hypersensitivity (Thorax, 2002; 57: 110-5), but other relaxation techniques can work as well.