The side effects of Botox injections

The side effects of Botox injections

The side effects of Botox injectionsBotulinum toxin (Botox) is a neurotoxin derived from the Clostridium botulinum bacterium, and injections of this toxin are used for treatment of facial wrinkles.  Botox is the treatment of choice for frown lines, horizontal forehead lines, and crow’s feet.  Botox injections into specific overactive muscles causes them to relax, and this softens the overlying skin and reduces wrinkles.

Botulinum toxin was first approved by the U.S. Food and Drug Administration (FDA) for cosmetic use in 2002 as Botox to treat frown lines, and in 2013 to treat crow’s feet; it is used off-label for all other cosmetic facial indications.

Although the procedure usually produces high patient satisfaction, side effects can occur, and there are also several contraindications to botulinum toxin injections.  A recent review highlights these side effects.


Contraindications to Botox injection include pregnancy or breastfeeding, sensitivity or allergy to constituents of the botulinum toxin product, body dysmorphic disorder, unrealistic expectations, dermatoses or infection in the treatment area, and keloidal scarring.  Other contraindications are gross motor weakness in the treatment area, neuromuscular disorder, and an immunocompromised   state.

Side effects

Complications with cosmetic Botox injections are uncommon, and are usually mild and temporary.

Injection reactions

Pain at the injection site can occur.  Small-gauge needles are used to minimize discomfort and bruising.  Mild erythema (redness of the skin), edema, and tenderness at injection sites can occur and usually resolve within a day. Bruising is common and some marks can be up to quarter-sized and can require up to two weeks to resolve. Ice applied to a bruise can minimize enlargement.  Patients are advised to discontinue aspirin and any medication or dietary supplement that has anticoagulant effects two weeks before treatment to minimize bruising.

Infection is rare but can occur.  Mild headaches can occur and usually resolve a few days after Botox injections.   Paresthesia (tingling) or dysesthesia (an unpleasant sensation) in the treatment area can occur, but this is rare, and could be caused by nerve trauma.

Anxiety or severe anxiety can occur.

Undesired botulinum toxin effects

A botulinum toxin injectable product with AbobotulinumtoxinA is contraindicated in patients with cow’s milk protein allergy because it contains bovine protein. Immediate hypersensitivity and allergic reactions may occur, and there may be edema, urticaria, and even anaphylaxis. Epinephrine and methylprednisolone would then be used, instead of diphenhydramine (Benadryl) because of its anticholinergic effects.

Temporary upper eyelid droop is uncommon, and is almost always unilateral, with a 2- to 3-mm lowering of the affected eyelid.  It may be treated using ophthalmic solutions, such as over-the-counter naphazoline 0.025%/pheniramine 0.3% or prescription apraclonidine 0.5% (Iopidine).  Apraclonidine should be used with caution because it can exacerbate or unmask underlying glaucoma.

Eyebrow ptosis (lowering) and undesired eyebrow shape can occur, but these are temporary. Facial asymmetry can also occur from uneven dosing of botulinum toxin.

Other rare complications include formation of antibodies.  Medications that inhibit neuromuscular signaling such as muscle relaxants, anticholinergics, aminoglycosides, and quinidine, may increase Botox effects.

Patients should avoid lying supine after the treatment for four hours, and are also advised to avoid massaging or applying heat to the treatment area.  Activities that cause flushing, such as exercising heavily, and consuming alcohol should also be avoided on the day of treatment.

Botox injections can help you improve your facial appearance and help you feel better about yourself.  Always advise your doctor of pre-existing conditions you have, especially any allergies you have, and have a list of the medications you use ready before any procedure.  Be aware of side effects that can occur.

This review used PubMed, Cochrane database, POEMs, Essential Evidence, the FDA website, aesthetic procedure textbooks, and UpToDate as data sources.   The search included meta-analyses, randomized controlled trials, clinical trials, and reviews.