Allergen-specific immunotherapy, in which an allergen is injected subcutaneously, is known to be an effective treatment against hay fever. But it is rarely used because it carries risks of allergic side-effects and requires up to 70 doctor visits over three to five years.

Swiss researchers injected 165 hay fever patients with pollen extract, giving either three injections into lymph nodes over two months or the standard 54 subcutaneous injections over three years.

Intralymphatic treatment quickly led to long-lasting tolerance to nasal provocation with pollen, equivalent to subcutaneous treatment.

After four months, patients who received injections into the lymph nodes required 10 times as much pollen to trigger nasal symptoms.

Patients injected subcutaneously did not start to show an increase in allergen tolerance until after a year of treatment.

In addition, in the first pollen season after treatment, 43 per cent of patients who received intralymphatic injections used antihistamine tablets, compared with 66 per cent of patients injected subcutaneously.

Injection into the lymph nodes was associated with fewer and less severe side-effects and was less painful.

Patients assigned to intralymphatic injection were also more likely to complete treatment. Only 32 of 54 patients assigned to standard subcutaneous injections completed the treatment, compared with all 58 assigned to intralymphatic injection.

'Intralymphatic immunotherapy allowed a marked reduction of both number and dose of allergen injections necessary to induce allergen tolerance, making the treatment shorter and safer,' the researchers say.

'The practically painless procedure also enhanced patient compliance, thus making intralymphatic immunotherapy an interesting alternative to conventional subcutaneous treatment.'

tom.moberly@haymarket.com

• PNAS 2008; 105: 17,908-12

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