Acidic diarrhoea: what it may mean and what to do

Rapid bowel transit can leave digestive substances in the stool and repeated wiping can worsen soreness. The underlying cause may be a short-lived gut infection, a food trigger, or an ongoing bowel problem, so the pattern and accompanying symptoms matter.

The word “acidic” describes how the stool feels on contact with the anus; it cannot identify its chemical acidity or cause. Frequent watery bowel movements expose delicate skin to moisture and digestive enzymes. Cramping, nausea, fever, recent travel, a new food, antibiotics, or symptoms that keep returning can help a clinician narrow the explanation.

Gastroenteritis and food poisoning can present with sudden diarrhoea, while giardiasis may follow contaminated food or water. Food intolerance, coeliac disease, Crohn's disease, irritable bowel syndrome, and hyperthyroidism can also present with recurrent loose stools, each with a different overall pattern.

Take frequent sips of water or an oral rehydration solution and continue light meals as tolerated. Avoid alcohol and foods that clearly make the episode worse. Do not prepare food for other people while you have diarrhoea, and wash your hands carefully after using the toilet.

Rinse irritated skin gently with lukewarm water, pat rather than rub, and apply a simple fragrance-free barrier ointment. A pharmacist can advise whether a diarrhoea medicine is appropriate; some products should be avoided when there is blood in the stool, fever, or suspected infection.

Seek urgent help for fainting, confusion, severe or worsening abdominal pain, black or bloody stool, inability to keep fluids down, or signs of marked dehydration such as very little urine and pronounced dizziness. Babies, older adults, pregnant people, and anyone with reduced immunity can become unwell more quickly.

Arrange a GP assessment if diarrhoea persists, repeatedly returns, wakes you from sleep, follows recent antibiotics or travel, or occurs with weight loss. Note when it began, stool frequency, possible food exposures, medicines, travel, and whether anyone around you is also ill.

Ask whether your symptoms suggest infection, a dietary trigger, medicine effects, or bowel inflammation; whether a stool or blood test is useful; how to replace fluids safely; and which skin products or diarrhoea medicines suit your situation.