Immunotherapy is an option for managing severe allergies, including severe SAR, but it is not suitable for everyone. NHS Choices discusses it as a possible option for when other interventions are not relieving symptoms. However, Allergy UK advises that few people with asthma will be considered for immunotherapy. As immunotherapy must be initiated in a specialist medical centre in case of anaphylaxis, there may also be a waiting list.

The principle is to introduce allergen pollen at a low level, allowing the body to develop a tolerance to the allergen. Therapy should commence three months before the onset of the pollen season, gradually increasing in dose as the body starts to respond. Treatment is usually repeated annually for three years before sufficient tolerance has developed, but will not be repeated after the first year if no improvement is recorded.

Either of the following two methods are used to introduce the allergen into the body:
€¢ Systemic (SIT) or subcutaneous (SCIT) injection immunotherapy
€¢ Sublingual immunotherapy (SLIT) administered as a sublingual tablet.
A joint US-UK meta-analysis suggests that immunotherapy can be beneficial. Six timothy grass SLIT-tablet trials (n=3,094) and two ragweed SLIT-tablet trials (n=658) were included and compared to montelukast, desloratadine and mometasone furoate nasal spray (MFNS).

€Although comparisons were limited by study design heterogeneity and use of rescue medications in SLIT-tablet trials, effects on nasal symptoms with timothy grass and ragweed SLIT-tablets were nearly as great as with MFNS and numerically greater than with montelukast and desloratadine for SAR,€ said the researchers.