Additive-induced urticaria: experience with monosodium glutamate (MSG).

Area of Science:

• Dermatology
• Allergy and Immunology
• Clinical Nutrition

Background:

• The role of food additives, including monosodium glutamate (MSG), in exacerbating chronic urticaria is not well-established.
• Previous studies investigating additive-urticaria associations often lack rigorous scientific design.
• The prevalence of reactions to additives in chronic urticaria patients requires further investigation.

Purpose of the Study:

• To determine the prevalence of reactions to common food additives, specifically MSG, in patients diagnosed with chronic idiopathic urticaria.
• To employ a stringent research protocol to objectively assess additive-induced urticaria.
• To provide reliable data on MSG as a potential trigger for chronic urticaria.

Main Methods:

• A cohort of 65 patients with chronic urticaria (>6 weeks duration) and no discernible etiology were enrolled.
• Patients were studied on stable, low-dose antihistamine therapy.
• A single-blind screening challenge with 11 common additives (including 2500 mg MSG) was followed by double-blind, placebo-controlled challenges for positive reactors.

Main Results:

• Two subjects exhibited positive reactions during the initial single-blind screening challenges.
• Neither of these two subjects showed a positive response during the subsequent double-blind, placebo-controlled rechallenge.
• This suggests a very low incidence of MSG-induced chronic idiopathic urticaria.

Conclusions:

• Monosodium glutamate (MSG) is an uncommon exacerbating factor in chronic idiopathic urticaria, affecting less than 3% of patients.
• The study utilized a rigorous protocol to validate findings, differentiating true reactions from placebo effects.
• These results contribute to a clearer understanding of dietary triggers in chronic urticaria management.