WHO identifies dehydration—the loss of water and electrolytes—as the most severe threat posed by diarrhoea. This resource summarizes general WHO information and does not assess an individual child.
How to read this guidance
Infections can overlap in their early symptoms, while severity can change with age, immunity, vaccination history and the site of infection. The useful first question is therefore not “Which label fits?” but “How unwell is the child, and is urgent assessment needed?”
The sections below retain the factual scope of the linked source. They add practical questions and safety-netting without claiming that a symptom, measurement or exposure proves a diagnosis in one child.
What WHO means by diarrhoea
WHO defines diarrhoea as the passage of three or more loose or liquid stools per day, or stools that are more frequent than is normal for the individual. WHO also notes that frequent formed stools are not diarrhoea and that loose, pasty stools in breastfed babies are not, by themselves, diarrhoea.
Why dehydration matters
WHO describes dehydration as the most severe threat posed by diarrhoea. Water and electrolytes are lost during a diarrhoeal episode, and dehydration develops when those losses are not replaced.
How WHO classifies dehydration
WHO’s diarrhoeal-disease information describes severe dehydration using combinations of clinical signs including lethargy or unconsciousness, sunken eyes, inability to drink or drinking poorly, and a skin pinch that returns very slowly. It describes some dehydration using combinations that include restlessness or irritability, sunken eyes, and drinking eagerly or being thirsty.
Oral rehydration information
WHO explains that oral rehydration salts (ORS) replace water and electrolytes lost in stool. WHO’s 2024 guideline recommends low-osmolarity ORS in children up to 10 years of age with acute watery diarrhoea and dehydration.
Food, hygiene and prevention
WHO identifies continued nutrient-rich foods, including breast milk, as part of diarrhoea care. Its prevention information includes safe drinking-water, improved sanitation, hand washing with soap, good personal and food hygiene, exclusive breastfeeding for the first six months of life, and rotavirus vaccination.
When WHO identifies professional assessment
WHO specifically identifies professional consultation in connection with persistent diarrhoea, blood in the stool, or signs of dehydration. For any concern relating to an individual child, consult a qualified doctor.
What to observe and record
- breathing effort and colour
- fluid intake, vomiting and urine output
- alertness, comfort and ability to interact
- the timing of fever, rash, pain or relevant exposure
Keep the record focused on the illness described above: onset, fever or pain pattern, relevant contact or travel, breathing, drinking, urine output, alertness and any rapid change. These details help a clinician compare the child’s course with the source-defined pattern without treating the checklist as a diagnosis.
Practical next steps
- use hand, respiratory, food, water or vector precautions that match the official source
- keep vaccination records available and follow the applicable national schedule
- offer appropriate fluids and ordinary food as tolerated
- seek testing or treatment advice rather than using leftover antibiotics
Use the prevention measures that the official source actually describes and follow local public-health advice when exposure or school attendance is relevant. Treatment and testing depend on the child and should come from a qualified professional; do not use leftover antibiotics or another person’s prescription.
When urgent assessment is needed
- difficulty breathing, blue or grey colour, or pauses in breathing
- a seizure, confusion, neck stiffness or difficulty waking
- severe dehydration, persistent vomiting or inability to drink
- rapid worsening, severe pain or a rash with serious systemic illness
Young infants and children with immune, heart, lung, blood, metabolic or neurologic conditions may need earlier assessment. Use local emergency services whenever delay could be dangerous.
Preparing for a healthcare visit
Ask which findings support the suspected infection, whether testing changes care, what prevention applies to contacts, and which change requires urgent reassessment. Bring the exposure and symptom timeline plus vaccination, medication and allergy information.
If safe, a photograph of a changing rash or brief video of an unusual movement can help show what happened outside the clinic. Never delay emergency care to make a recording. For a possibly contagious illness, telephone ahead before entering a shared waiting area.
Following the plan at home
Make sure every caregiver understands the same plan. Record meaningful changes rather than checking constantly, protect rest and hydration, and keep follow-up appointments. Improvement in one symptom does not cancel a new red flag, while one mild symptom in an otherwise well child does not establish a serious condition.
Before leaving a visit, repeat the plan back in your own words: what to do today, when to follow up, whether school or childcare attendance should change, and where to go if the child worsens outside normal clinic hours.
Questions this page cannot answer for one child
This page cannot confirm the organism, site of infection, contagious period or treatment for an individual child. Similar early symptoms can have different causes, and severity depends on examination, age, immunity, exposure and the child’s current condition.
Ask the healthcare professional how the child’s age and medical history change the interpretation, what alternative explanations remain possible, and whether observation, testing, referral or treatment is appropriate. When no test is needed, ask what expected improvement should look like and how long it is reasonable to wait.
Document who provided the advice, the planned review time and any agreed precautions so that another caregiver or service can understand what has already been assessed.
If the family faces language, transport, cost or access barriers, mention them directly. A safe plan must be practical enough to follow, and the service may be able to adjust timing, written instructions or referral arrangements.
Keep the original source link and review date with the notes so later readers can distinguish the published evidence from the individualized clinical plan.
Limits and source boundaries
Read the publication date and scope of the source. A global fact sheet may describe burden and prevention without providing a local treatment pathway; a surveillance or screening page may describe population practice without estimating one child’s risk.
Recommendations, schedules and available services differ by country and can change. Use the official source for its stated evidence and a qualified professional for decisions about the individual child.