Introduction and purpose Botulinum toxin (BoNT) products are commonly used to treat muscle spasms such as cervical dystonia as well as to treat expression lines. Serotype A of botulinum toxin is the strongest and is used in aesthetic medicine procedures. It provides predictable results while having few side effects. Nevertheless, complications may occur, such as: ptosis of the upper eyelid, drooping eyebrows, ectropia, double vision, xerophthalmia, falling corners of the mouth, dysphagia, hoarseness, local swelling, erythema, bruising, pain at the injection site, asymmetry. The aim of the study is to discuss the most common complications after injection of the botulin toxin in the correction of mimic wrinkles. Description of the state of knowledge BoNT is a neurotoxin that acts on the neuromuscular junctions, inhibits the release of acetylcholine, consequently causing temporary chemical denervation. Muscle function begins to return approximately 3 months after injection and fully returns after 6 months. Comparison of clinical trials of botulinum toxin type A in aesthetic allowed for the quantification of the frequency of adverse effects:drooping eyelids (2.5%), drooping eyebrows (3.1%), disturbed eye sensation (3%) and lip asymmetry (6.9%). Complications after cosmetic botulinum toxin injections are rare, and those that do occur are usually mild and transient. These complications are technique dependent; the incidence decreases as the injection ability improves. Summary Side effects are rare, nevertheless, thorough knowledge of the patient's anatomy, medical history, possible complications related to the specific product and site of administration, and close monitoring are essential for safe, effective treatment and the achievement of satisfactory results.