Why Does My Ostomy Bag Keep Leaking? Causes and How to Prevent It

A leaking bag is one of the most common ostomy worries, and it is honest to say leaks do happen, especially in the first weeks while you are still learning your kit. The reassuring part is that a leak is almost always a fit problem with a practical fix, not something you simply have to live with.

Why Bags Leak

Most leaks start at the seal. The Peristomal Skin Assessment Guide for consumers, published by the Wound, Ostomy and Continence Nurses (WOCN) Society, explains that a pouch leaks when the skin barrier opening does not fit closely around the base of the stoma, which lets output slip under the seal and loosen it (WOCN consumer guide). A few things make that more likely:

The opening is the wrong size or shape. A stoma can change shape and size in the weeks and months after surgery, so an opening that fit last month may be too large now. The WOCN guide advises measuring your stoma routinely and checking the barrier opening against it, and examining your stoma both standing and sitting, because the surface can change with position.

The skin around the stoma is not flat. Creases, folds, scars, or a stoma that sits flush or pulls inward all leave gaps the adhesive cannot bridge. Colostomy UK lists changes in the shape or size of the stoma, weight changes, and skin creases or scarring among the common reasons a seal fails (Colostomy UK).

Moisture and heat. Skin that was damp when the bag went on, or heat and sweat during the day, can weaken the adhesive so the seal gives way sooner than expected.

Why Repeated Leaks Matter

A leak is uncomfortable and can knock your confidence, but it also matters for the skin. A 2025 prospective observational cohort study in the journal Nursing Reports notes that peristomal skin complications often arise from continuous exposure of the skin to output leaking under the barrier. In that study, a structured prevention protocol was associated with low complication rates, around 8.5 percent at 30 days, compared with published benchmarks of roughly 35 to 73 percent (Nursing Reports, 2025). As a single cohort study this shows an association rather than proof, but it lines up with a consistent message across the guidance: stopping leaks early protects the skin.

What Actually Helps

The fixes follow from the causes, and none of them require a particular brand.

Size the opening to your stoma. Cut or mould the barrier opening to match the current size and shape of your stoma, so output goes into the bag instead of under it. Re-measure if your weight or your stoma has changed.

Start with clean, dry skin. Colostomy UK advises cleaning the skin around the stoma with warm water only and making sure it is fully dry before applying a new pouch.

Create a flat surface. Where there are dips, creases, or a flush or retracted stoma, the WOCN guide suggests considering a barrier ring, a convex pouching system, and/or an ostomy belt to help the seal sit flat and snug. Colostomy UK similarly notes that a seal, or even a different type of pouch, can help create a flat surface around the stoma.

Manage moisture. If the skin is waterlogged, the WOCN guide describes dusting it lightly with stoma powder and brushing off the excess, then stopping the powder once the skin recovers. In hot weather or with heavy sweating, changing the pouch a little more often can prevent the adhesive from giving way.

Night Leaks

Leaks that happen overnight often come down to output collecting while you lie flat and sleep for several hours. Emptying the bag before bed so it does not get too full, and changing to a fresh appliance on a regular schedule rather than waiting for a problem, are practical habits many people find help. If night leaks keep happening, it is worth raising with your stoma care nurse, who can look at whether the appliance or routine needs adjusting.

When to Ask for Help

You do not have to put up with repeated leaks. The WOCN guide suggests contacting a stoma or WOC nurse if there is no improvement after about seven days of trying to manage it yourself, or if you cannot keep a pouch sealed for 24 hours. Colostomy UK makes the same point plainly: you do not have to put up with sore skin or leakages, and your stoma care nurse or supplier can advise. A change of product or a small technique tweak often fixes it.

If your ostomy bag keeps leaking and you cannot work out why, speak to your stoma nurse or doctor, who can assess your pouching system and skin and help correct the cause.