At a glance
If you are considering botox injection for a chronic anal fissure, the question of incontinence may be on your mind — particularly if you have read about incontinence risk after LIS surgery. It is a reasonable concern. Understanding what the research actually shows about botox and continence helps put the risk in perspective.
The short version: botox temporarily relaxes the sphincter muscle. Some people experience minor, temporary changes in gas control while the botox is active. These changes resolve as the botox wears off. Permanent incontinence from botox is not a recognised pattern in the published research.
This guide covers what the evidence says, what people describe, how the risk compares to LIS, and what factors might affect your individual experience.
How botox affects the sphincter
To understand the continence question, it helps to understand what botox does.
The internal anal sphincter is a smooth muscle that maintains resting tone — the baseline tightness that helps keep the anal canal closed. In people with chronic fissures, this muscle is often in chronic spasm. That spasm restricts blood flow to the fissure and prevents healing.
Botox works by temporarily blocking the nerve signals that tell the muscle to contract. The sphincter relaxes. Blood flow improves. The fissure has a better chance to heal.
The key word is temporarily. The botox effect builds over the first one to two weeks and typically lasts two to three months. As the effect wears off, the nerve signals resume and the muscle returns to its normal resting tone.
This is fundamentally different from LIS, where a portion of the muscle is permanently divided. Botox does not cut anything. It does not permanently alter the structure of the sphincter. The muscle remains intact throughout.
What the research says
Published studies on botox for fissure report continence outcomes with varying levels of detail. Here is what the evidence generally shows.
Minor continence changes are reported by a minority
When studies ask about any change in gas control, urgency, or soiling during the botox active period, reported rates range from roughly 5 to 20 percent depending on the study and how the question is asked.
These numbers deserve context. The changes reported are overwhelmingly minor — primarily reduced gas control or a slight increase in urgency. They occur during the period when the botox is actively relaxing the sphincter, which is the same period when the fissure has its best chance to heal.
Gas control is the most common change
The most frequently reported continence change is reduced ability to hold gas. This is consistent with the mechanism — the resting tone of the sphincter is deliberately reduced, and gas control is one of the functions that depends on that resting tone.
People describe:
- Gas passing with less warning than usual
- Reduced ability to hold gas in situations where they previously could
- Needing to be slightly more aware of gas sensations
These changes are described as manageable rather than disabling. They represent a temporary reduction in a specific function, not a loss of continence in the way most people imagine when they hear the word.
Fecal incontinence is rare
Involuntary loss of stool — fecal incontinence — is uncommonly reported after botox for fissure. When it is reported, it is typically minor (small amounts with urgency rather than complete loss of control) and temporary.
The research literature does not identify botox injection for fissure as a significant cause of fecal incontinence. This distinguishes it clearly from LIS, where a small but recognised percentage of people experience lasting continence changes.
Changes are temporary
This is the most important finding. Published follow-up data consistently shows that continence changes associated with botox resolve as the botox effect wears off. The sphincter returns to its pre-treatment tone. Gas control returns to baseline. Urgency normalises.
The typical timeline for resolution: two to three months after injection, aligned with the natural duration of the botox effect. Some people describe full return of control sooner; a few describe it taking slightly longer.
What people describe
Beyond the research data, what do people actually report about their experience?
The common experience
Most people who have botox for a fissure describe no meaningful change in continence. The sphincter relaxes, pain decreases, bowel movements become easier — and bowel control remains intact.
Among those who do notice a change, the pattern is consistent:
- Gas control is slightly reduced for a few weeks
- They adapt quickly to the change
- It resolves on its own as the botox wears off
- In retrospect, it was a minor aspect of the overall experience
The experience people worry about but rarely have
The fear of fecal incontinence — the image of having an accident in public, of needing to wear protection, of losing control entirely — is present for some people before the procedure. This fear is understandable, particularly for people who have read about incontinence risk after LIS and apply those concerns to botox.
In practice, this scenario is not what people describe. The temporary relaxation of the sphincter from botox does not produce the type of profound continence loss that the word “incontinence” conjures. It produces, at most, a minor and temporary reduction in one specific function — gas control — while leaving overall bowel control intact.
What people say afterward
People who experienced minor gas control changes during the botox active period overwhelmingly describe it as:
- A minor inconvenience, not a significant problem
- Something they barely thought about compared to the fissure pain
- A trade-off they would make again without hesitation
- Resolved completely once the botox wore off
How this compares to LIS incontinence risk
The comparison between botox and LIS continence risk is one of the most important conversations in fissure treatment decisions. The differences are fundamental.
Duration of any effect
- Botox: Temporary. Any continence change resolves as the botox wears off (2 to 3 months).
- LIS: Potentially permanent. The sphincter is structurally altered by the procedure.
Mechanism
- Botox: Chemical relaxation. No structural change. The muscle remains intact.
- LIS: Surgical division. A portion of the muscle is permanently cut.
Reversibility
- Botox: Fully reversible. The muscle returns to its pre-treatment function.
- LIS: Not reversible. The divided muscle does not regenerate.
Severity of reported changes
- Botox: Overwhelmingly minor and limited to gas control.
- LIS: Mostly minor (gas control), but with a small risk of more significant and lasting changes including fecal incontinence in a minority of people.
This comparison is one reason some surgeons prefer botox — alone or combined with fissurectomy — as a first-line approach before considering LIS. The continence risk profile is meaningfully different.
For people with additional risk factors for incontinence — previous anal surgery, multiple vaginal deliveries, older age, pre-existing sphincter weakness — botox offers a way to attempt healing without permanently altering the sphincter.
Risk factors that may affect your experience
While botox continence effects are temporary for essentially everyone, some factors may influence whether you notice any change at all:
- Pre-existing sphincter weakness — if the sphincter is already functioning at reduced capacity, the additional relaxation from botox may be more noticeable
- Dosage — higher doses of botox produce more relaxation. Your surgeon selects the dose based on your situation.
- Previous procedures — if you have had prior surgery that affected the sphincter, there may be less reserve capacity
- Multiple injections — repeated botox treatments are generally well tolerated, but cumulative effects on the sphincter are worth discussing with your surgeon
These factors do not make botox unsafe. They are part of the clinical assessment that your surgeon uses to determine the right approach for your specific situation.
The fear vs the reality
It is worth stating directly: the fear of incontinence from botox is disproportionate to the actual risk for most people.
This fear is understandable. The word “incontinence” carries enormous emotional weight. It connects to deeply held anxieties about bodily control, dignity, and vulnerability. When people hear that any procedure might affect continence, the imagination goes to the worst case.
For botox, the worst case is: minor, temporary gas control reduction that resolves in a few weeks. That is a meaningful gap between the fear and the reality.
This does not mean the concern should be dismissed. It means it should be discussed honestly — with your surgeon, in the context of your specific history and anatomy. Understanding that botox continence effects are temporary, minor when they occur, and resolve on their own is the foundation for an informed decision.
What to discuss with your surgeon
If incontinence risk is a concern — and for many people it is — these questions can help frame the conversation:
- What continence changes do you typically see in your patients after botox?
- Given my specific history, is there any reason to be more cautious?
- If I do notice a change in gas control, how long would you expect it to last?
- How does the continence risk of botox compare to LIS in your experience?
- Would fissurectomy with botox change the risk profile compared to botox alone?
Your surgeon’s individual experience and data are more relevant to your decision than published averages. Ask for their perspective specifically.
Talking to your doctor
If you are currently weighing botox as a treatment option for a chronic fissure, bring the continence question to your appointment. A good surgeon will not dismiss it. They will explain the temporary nature of the effect, contextualise the risk for your situation, and help you understand what to expect.
If you have already had botox and are experiencing gas control changes that concern you, know that this is a recognised and temporary effect. It typically resolves as the botox wears off. If it persists beyond three to four months, or if you are experiencing fecal incontinence rather than gas control changes, speak with your surgeon for assessment.
If you are trying to organise your thoughts about botox treatment, our AI experience navigator offers a private, anonymous space to talk through what you are considering. It does not give medical advice, but it can help you clarify your questions and prepare for your appointment.