A Double Blind Placebo Controlled Randomised Trial to Study the Effects of Birch Pollen Specific Immunotherapy (BP-SIT) on the Symptoms of the Oral Allergy Syndrome in Adult Patients

Birch pollen allergy is increasingly common. It causes asthma and early season hay fever. This is because the body recognises birch pollen and reacts to it, leading to symptoms. Many patients with birch allergy get an itchy and/or swollen mouth when they eat fresh fruit (apples, pears, peaches, plums etc). Some fruit proteins have a similar structure to birch pollen; because of this the body recognises these proteins too causing the immune system to respond. This response causes symptoms of itch and swelling inside the mouth and throat. the investigators want to find out whether it is possible to get rid of the fruit-induced symptoms by using a desensitisation procedure that has been developed for treating the kind of hay fever that is caused by birch pollen. Desensitisation involves giving a small injection of pollen just under the skin and gradually increasing the amount each week. This allows the body to build up a "tolerance" to the injected protein. When the pollen is then encountered in real life the immune system reacts less vigorously so symptoms are less severe. This treatment does reduce hay fever symptoms. Our study aims to find out if this tolerance is transferred to the fruit proteins enabling patients to eat apples with minimal symptoms. Patients will be given apple to eat in a hidden form before treatment and their response assessed. They will then receive either active or dummy pollen injections before birch pollen season. A few months after completing these injections they will have another disguised apple test to see whether their symptoms are any better. If symptoms have improved with treatment then this therapy could be offered to patients in the future. This would allow them to eat fresh fruit without worrying about unpleasant symptoms and improve their hay fever symptoms.