What are the most common side effects of Botox?
The most common are mild pain at the injection site, redness, small bumps, bruising and a temporary headache. They mostly relate to the needle and the fluid in the tissue rather than to the toxin itself, and they usually settle quickly.
With any fine-needle injection there is a chance of touching a small vessel, which can cause bruising, particularly in thin-skinned areas such as around the eyes. Small raised bumps are usually due to the fluid settling in the tissue and typically fade within one to a few hours. A headache can be reported in the first days, especially after forehead and between-the-brow treatment, and most often passes by itself.
How long bruising and swelling last varies from person to person, from a day or two to longer. Blood-thinning medication or some supplements can increase the tendency to bruise, so you should tell the doctor about everything you take. See the page on bruising and swelling for the factors involved.
What less common side effects can occur after Botox?
Less commonly, a temporary difference between the two sides, a heavy feeling in the brow, a drooping eyelid, dry or watery eyes, and a change in the smile after lower-face treatment can occur. They relate to a limited effect on muscles outside the intended area and improve over time.
Because Botox weakens muscle, the look can change in an unintended way if the dose or injection points do not suit the area, or if the toxin reaches a neighbouring muscle. Over-relaxing the forehead can make the brows feel heavy, and between-the-brow treatment can rarely lead to a drooping eyelid. In the lower face and around the chin, there can be a temporary change in smiling or mouth movement. These effects fade gradually as the toxin wears off, which can take several weeks.
The risk is reduced by a doctor who knows facial muscle anatomy, adjusts the dose to the area and person, and avoids unnecessarily high doses. For details on eyelid droop see the page on a droopy eyelid after Botox. If you notice something like this, contact the treating doctor rather than trying to manage it yourself.
How long do Botox side effects last?
Redness, swelling and headache from the injection usually pass within hours to a few days. Effects linked to muscle weakness, such as asymmetry or eyelid droop, improve as the toxin wears off and can last weeks. Duration varies with the person, the area and the dose.
Because the effect of Botox cannot be reversed, there is limited scope for action once a muscle-related effect appears; it generally improves by itself as the toxin fades. This is typically a matter of weeks but varies between people, and giving an exact number of days would not be accurate. Any symptoms during this waiting period are assessed at a review visit.
In some cases supportive steps may be considered; these are decided by the doctor after an examination, and any drops or medicine are a doctor decision. Attending the review visit at around two weeks lets you assess the result together and plan for any difference that can be adjusted.
Which symptoms after Botox need urgent assessment?
Difficulty swallowing, speaking or breathing, widespread muscle weakness, marked vision problems, swelling of the face or throat and a widespread rash need urgent medical assessment. They are very rare, but they are not to be waited out, and you should seek care without delay.
Very rarely, symptoms linked to spread of the toxin away from the injection site have been reported. These include difficulty swallowing, breathing or speaking, general weakness, blurred or double vision. They can appear days to weeks after treatment and can also signal an allergic reaction or another health problem. If this happens, go to emergency services without delay and say that you had a Botox treatment.
Redness, warmth, pain or discharge at an injection site that keeps increasing may suggest infection and should be reported to the doctor. In these situations no home medicine or method is recommended; assessment is made by the treating doctor or emergency services. For general information see the page on warning signs.
Who needs a more careful assessment of side-effect risk?
During pregnancy or breastfeeding, with nerve or muscle diseases, with infection at the injection site, with allergy to the product or its contents and while taking blood thinners, Botox is either not done or planned more carefully. The decision is made at consultation after a medical history.
Botox affects nerve-to-muscle signalling, so conditions that disturb this communication call for extra caution. There is not enough data to support its safety during pregnancy and breastfeeding, so it is generally not done then. It is also not advised for people who have had an allergic reaction to the toxin or its contents.
Sharing your medicines, supplements, past treatments and illnesses lets the risk be judged more accurately. Using an original, licensed product and a qualified doctor is the basis of managing side-effect risk; see the pages on contraindications and product authenticity. A consultation is all you need to arrange an assessment.
Frequently asked questions
Is a headache after Botox normal?
A mild headache can be reported in the first days, especially after forehead and between-the-brow treatment, and mostly passes by itself. If it is severe, lasts for days or comes with vision changes, contact the treating doctor.
How long does bruising after Botox last?
Bruising mostly fades within a few days and can last longer in some people. It depends on factors such as thin skin, blood-thinning medication and personal tendency. Tell the doctor if swelling or pain keeps increasing.
What happens if my face looks asymmetrical after Botox?
The effect may not settle at the same speed on both sides, so about two weeks are allowed. If a difference remains, muscle strength and injection points are assessed at a review and a small correction may be planned. Massaging the area yourself is not advised.
Can you be allergic to Botox?
It is possible, although rare. Widespread redness, itching, swelling of the face or throat or shortness of breath may signal an allergic reaction and need urgent assessment. Tell the doctor beforehand if you have had one.
Do Botox side effects become long-term?
The effect of Botox is temporary, and muscle-related side effects improve as the toxin wears off. Duration varies by person and area. A condition that lasts long or worsens needs to be reassessed by a doctor.
What can reduce the risk of side effects?
Sharing your full medical history and medicines, choosing a qualified doctor, making sure the product is original and following the aftercare advice all help. Dose and injection points are planned for the area and the person.
Sources (5)
- U.S. FDA (DailyMed, NLM): BOTOX COSMETIC- onabotulinumtoxina injection, powder, lyophilized, for solution (Prescribing Information and Medication Guide) (2026)
- Global Aesthetics Consensus Group (Sundaram et al., Plast Reconstr Surg): Global Aesthetics Consensus: Botulinum Toxin Type A--Evidence-Based Review, Emerging Concepts, and Consensus Recommendations for Aesthetic Use, Including Updates on Complications (2016)
- MHRA-approved SmPC via emc (Galderma): Azzalure, 125 Speywood units, powder for solution for injection - Summary of Product Characteristics (SmPC)
- Freixo et al., Cureus: Management of Complications Following Botulinum Toxin Facial Injections: A Narrative Review (2026)
- U.S. CDC: How to Stay Safe When Getting Botulinum Toxin Injections (2026)
This content is for general information and does not replace a personal medical assessment.