Allergy to cow's milk is the most common food allergy affecting children. There is currently no accepted routine clinical therapy to cure milk allergy. Recently studies have attempted to induce desensitisation using small daily doses of cow's milk, predominantly by the oral route (oral immunotherapy, OIT). Although this therapy works for some people, its effects are not generally long lasting and it is associated with significant side effects during protocol, including potentially life-threatening allergic reactions.

Pilot data suggests that sublingual immunotherapy (SLIT, where allergen is held under the tongue, rather than swallowed) can also induce a degree of desensitisation, but with fewer adverse events. However, the degree of desensitisation induced appears to be lower than that with oral immunotherapy.

The investigators wish to determine whether a sublingual pretreatment phase can improve the safety of conventional OIT in cow's milk allergy.

Inclusion Criteria:

1. Allergic to 1.44g CM protein (approx. 40ml fresh milk) or less, at DBPCFC prior to randomisation
2. Informed consent of parent/legal guardian, patient assent where possible

Exclusion Criteria:

1. Required previous admission to an intensive care unit for management of an allergic reaction.
2. Significant symptoms of non---IgE---mediated CM allergy within the previous 12 months.
3. Children with a past history of CM allergy currently consuming CM-containing products other than extensively--heated milk in baked foods (e.g. biscuits, cakes).
4. Poorly controlled asthma within the previous 3 months (as defined by clinician judgement with reference to the ICON consensus), or asthma requiring treatment with >5 days oral corticosteroids within the previous 3 months.
5. Moderate---severe eczema, defined as requiring more than once daily application of 1% hydrocortisone as maintenance treatment despite appropriate use of emollients (eczema is not otherwise an exclusion criteria)
6. Clinically significant chronic illness (other than asthma, rhinitis or eczema)
7. History of symptoms of eosinophilic oesophagitis, irrespective of cause
8. Undergoing specific immunotherapy to another allergen and within the first year of treatment.
9. Receiving anti--IgE therapy, oral immunosuppressants, beta---blocker or ACE inhibitor.
10. Pregnancy
11. Unwilling or unable to fulfil study requirements