NHS information about sudden confusion (delirium), including how to tell if someone is confused and when to get medical help.
Find out about swelling in the ankles, feet and legs (oedema), including what it looks like, common causes and what to do about it.
Read about salivary gland stones (calculi), which are small stones that can form in your mouth. Find out how to try to remove them and when to get medical help.
Sarcoidosis is a rare condition that causes small patches of swollen tissue, called granulomas, to develop in the organs of the body.
Find out about scarlet fever, including the symptoms, what to do if you or your child has it, how it's treated, how long it lasts and how it's spread.
Read about schistosomiasis, also known as bilharzia, an infection caused by a parasitic worm that lives in fresh water in subtropical and tropical regions.
Read about scleroderma, including the different types, symptoms, causes and treatments.
Read about septic arthritis, which is a serious type of joint infection that should be treated straight away.
Read about sexually transmitted infections (STIs), including possible symptoms, common types of STI and when to go to a sexual health clinic.
Find out what shin splints are, how they happen, and what you can do about them.
NHS information about shortness of breath, or breathlessness, including when to get medical help and what the cause might be.
Shoulder impingement is a common cause of shoulder pain. Find out about the symptoms, causes and treatments for it.
Find out about sick building syndrome (SBS), including symptoms, things you can do to ease symptoms and possible causes.
Find out about silicosis, a long-term lung disease caused by inhaling large amounts of crystalline silica dust, usually over many years.
Find out about skin cysts, which are round, fluid-filled lumps under the skin. Read about the symptoms, treatments, types and causes.
Find out about skin tags, including what they look like, when and where to get medical help and how they’re treated.
Find out about slapped cheek syndrome (also called fifth disease), including symptoms and how to treat it.
Read about sleepwalking, including why it might happen, what you can do about it and when to get medical advice.
Find out about smelly urine, which on its own is not usually a cause for concern. Find out what can cause smelly pee and how to keep it clear and smelling mild.
Find out about what to do if you or someone you know is bitten by a snake.
Find out how to look after your lips when they're exposed to the sun, wind and cold.
Find out how to treat a sore or white tongue and read about the possible causes such as geographic tongue, oral thrush and mouth ulcers.
Find out what can cause a sore throat, how you can soothe it and when to get medical advice.
Read about what a spirometry test involves and why it's carried out.
Find out NHS information on spleen problems, splenectomy and living without a spleen.
Find out about spondylolisthesis, where a bone in the spine (vertebra) slips out of position, including what the symptoms are and how it's treated.
Read about some of the main types of Staphylococcal infections, including how they're spread and how they're treated.
Find out about steroid inhalers, including why they're used, who can use them, and what side effects they can cause.
Steroid injections, also called corticosteroid injections, are anti-inflammatory medicines used to treat a range of conditions. They can be used to treat problems such as joint pain, arthritis, sciatica and inflammatory bowel disease.
Find out about steroid nasal sprays, including why they're used, how to use them and possible side effects.
Find out what steroids (corticosteroids) are, when they're used, how they work, and what different types are available.
Steroid tablets, also called corticosteroid tablets, are a type of anti-inflammatory medicine used to treat a range of conditions.
Find out about Stevens-Johnson syndrome, including what causes it, what the symptoms are and when to get medical help.
Read about a stomach ache and abdominal pains, including stomach cramps or an ache in the tummy (abdomen).
Find out about the medicines that can help if you want to stop smoking, including nicotine replacement therapy (NRT) and bupropion (Zyban).
Find out about stretch marks, including where, when and how you get them, what causes them, and how they can be treated and prevented.
Find out about styes, including what causes them, what you can do to treat them and when to see a GP.
Sudden infant death syndrome (SIDS) – sometimes known as 'cot death' – is the sudden, unexpected and unexplained death of an apparently healthy baby.
Find out about sunburn, including what you can do to treat it yourself and when to get medical help.
Read about swollen lymph glands, which are usually a sign of infection. Find out what the symptoms are, how to ease them and when to get medical help.
Find out about skin abscesses, including how they look and feel, what treatment you may need, and what causes them.
Find out about scabies, including symptoms, causes and treatments.
Find out about scars, including types of scars, things you can do to improve how a scar looks, and treatments that may be recommended if a scar is severe.
Read about sciatica, which is pain caused by irritation or compression of the sciatic nerve. Find out about the symptoms, what you can do to ease the pain, and when to get medical help.
Find out what scoliosis is, why it happens and how it's treated.
Read about scurvy, a vitamin C deficiency caused by not eating foods (fruit and vegetables) rich in vitamin C over a long period of time.
NHS information about the symptoms of sepsis in children and adults, and where and when to get help.
Find out about shingles, including symptoms and what to do if you think you have it.
Find out more about short-sightedness (myopia), including the signs and how it’s usually treated with glasses or contact lenses.
Find out how you can relieve shoulder pain, what can cause it and when to get medical advice.
Find out about sickle cell disease, a serious inherited blood disorder where the red blood cells develop abnormally. Find out about the symptoms, causes and treatments.
Read about Sjögren's syndrome, which affects parts of the body that produce fluids, like tears and spit (saliva). Find out what the symptoms are, what causes it, how it's treated and advice about living with it.
Find out about sleep paralysis, a temporary inability to move or speak that happens when you're waking up or falling asleep.
Find out about slipped disc, including what it is, what causes it, how it's diagnosed and treated, plus how to prevent it.
Find out what you can do if you snore, why it happens, when to get medical help and what treatments can help.
Read about spina bifida, which is a condition where an unborn baby's spine and spinal cord does not develop properly.
Read about spinal muscular atrophy (SMA), a condition that makes the muscles weaker and causes problems with movement that get worse over time.
Sprains and strains are common injuries affecting the muscles and ligaments. Most can be treated at home without seeing a GP.
Find out what causes a squint and how it's treated. Also, read about the signs to look for in your child and when to see a doctor.
Stammering, or stuttering, affects speech and is relatively common in childhood. It can also persist into adulthood.
Read about statins – medicines that lower the level of low-density lipoprotein (LDL) cholesterol in the blood. Find out why you may be offered them, how they're taken, and the possible side effects.
Read about stem cell or bone marrow transplants, including why they're used, what's involved, and what the potential risks are.
Read about stillbirth, which is where a baby is born dead after 24 completed weeks of pregnancy. Find out the causes of stillbirth and how to reduce the risk.
Find out more about stomach cancer, including the symptoms, causes, tests, treatments and where to get help and support.
Stomach ulcers, also known as gastric ulcers, are open sores that develop on the lining of the stomach. Read about the possible symptoms, causes, treatments and complications.
Read about strokes, a serious and life-threatening medical condition that occurs when the blood supply to part of the brain is cut off.
A subarachnoid haemorrhage is an uncommon type of stroke caused by bleeding on the surface of the brain. It's a very serious condition and can be fatal.
Read about subdural haematoma, a serious condition where blood collects between the skull and the surface of the brain. Find out why it happens, what the symptoms are, and how it's treated.
Read more about supraventricular tachycardia (SVT), which is a condition where your heart suddenly beats much faster than normal. SVT is not usually serious but some people may need treatment.
Syphilis is a sexually transmitted infection (STI). Find out what the symptoms are, when and where to get medical help and how it's treated.
Read about soiling, which is when a child regularly poos their pants. Find out why it happens and what to do about it.
Find out about sinusitis, including the symptoms, how to treat it yourself, how a pharmacist can help, when to see a GP and the treatments they may recommend.
Find out about the causes of swollen arms and hands, what to do about it and when to get help.
Find out about sleep apnoea, which is when your breathing stops and starts while you sleep.
Find out what usually causes smelly feet and ways to treat them yourself.
Find out about strep A infections, including what the symptoms are, when to get medical help and how mild and severe strep A infections are treated.
Find out more about soft tissue sarcoma, its symptoms, when to get medical help, testing and diagnosis, treatment and where to find help and support.
Find out about selective mutism, an anxiety disorder that prevents people from speaking in certain social situations.
Read about seasonal affective disorder (SAD), a type of depression that recurs on a seasonal basis. Find out about the symptoms, causes and treatments.
Read about skin picking disorder, where you cannot stop picking at your skin. There are things you can try to help yourself, but some people may need professional treatment.
Find out about social anxiety (social phobia), including the symptoms, getting treatment and what you can do yourself to help overcome it.
Self-harm is when somebody intentionally damages or injures their body and is a sign of emotional distress. Support is available for anyone who self-harms or thinks about self-harm, as well as their friends and family.
Find out about the shingles vaccine, including who it's for, how to get it and possible side effects.