Background The same dosing schedule, 1000 SQ-U times three, with one-month intervals, have been evaluated in most trials of intralymphatic immunotherapy (ILIT) for the treatment of allergic rhinitis (AR). The present studies aimed to evaluate if a dose escalation in ILIT can enhance the clinical and immunological effects, without compromising safety. Methods Two randomized double-blind placebo-controlled trials of ILIT for grass pollen induced AR were performed. The first included 29 patients that had recently ended 3 years of SCIT and the second contained 39 not previously vaccinated patients. An up-dosage of 1000-3000-10 000 SQ-U with one month in between was evaluated. Results ILIT in doses up to 10 000 SQ-U was safe after recent SCIT. The combined symptom-medication scores (CSMS) were reduced by 31% and the grass specific IgG4 levels in blood were doubled. In ILIT de novo, the two first patients that received active treatment developed serious adverse reactions at 5000 SQ-U. A modified up-dosing schedule; 1000-3000-3000 SQ-U appeared to be safe but failed to improve the CSMS, quality of life and nasal provocation response. Flow cytometry analyses could not detect any T-cell changes, while lymph node derived dendritic cells showed increased activation. Conclusion ILIT in high doses after SCIT appears to further reduce grass pollen induced seasonal symptoms and may be considered as an add-on treatment for patients that do not reach full symptom control after SCIT. Up-dosing schedules de novo with three monthly injections that exceeds 3 000 SQ-U should be avoided.