A comparative cohort study published in the journal Plastic and Reconstructive Surgery examined the effect of climate on the dosage requirements for botulinum toxin A to the glabella.

The low sun exposure center included 231 patients (women aged 35 to 60 years) who received treatment in the United Kingdom during the winter months. The high sun exposure center included 292 patients from the same age demographic who received treatment in the Malta summer months.

A multivariable analysis showed that the low-sun group had lower total dose requirements, with mean total doses (in units) significantly higher in the high-sun group. Researchers conclude that patients injected with botulinum toxin A to the glabella in high-sun climates may have significantly increased dose requirements to achieve maximal paralysis.

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