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.

Inclusion Criteria:

• Male or female; age 18 with no upper age limit
• History of typical fruit-related symptoms on eating apples plus or minus other plant-derived foods known to be involved in the pollen-food syndrome
• History of spring rhinitis hay fever
• Positive skin prick test to birch pollen
• Positive open food challenge to apple

Exclusion Criteria:

• Significant medical conditions that may affect the risks of giving BP-SIT (especially uncontrolled asthma or ongoing need for beta-blockers)
• History of moderate to severe systemic reaction to apple, defined as any of: generalised urticaria, generalised angioedema, history convincing for laryngeal oedema, collapse
• Current immunological disease (auto-immune or thyroid disease, immunodeficiency)
• Malignant disease within the past five years (Patients with previous malignant disease that is considered cured, may be included subject to the consent of their oncologist)
• Inability to attend regularly for injections and follow-up visits
• Severe atopic dermatitis
• Previous immunotherapy with birch pollen extract
• Pregnant or not using adequate contraception (post-menopausal, surgically sterilised, long-term abstinent, or barrier methods plus spermicide)
• Breast-feeding
• Evidence of current drug or alcohol misuse