In rare cases there may be skin irritation or infection, slight swelling or a small bruise. Therefore, no blood-thinning medication should be taken at least 1 week before the treatment. Very rarely a temporary lowering of the upper eyelid, eyebrow, tears, headache, dry mouth, tiredness, numbness or a general feeling of illness may occur. All side effects are transient according to current knowledge. Botulinum toxin must not be used in patients with nerve or muscle disorders or in patients with known pregnancy.