Balanitis is a skin irritation on the head of the penis that can affect men and boys. It's not usually serious, but you should see a GP if you think you or your son has balanitis.
Read about having a barium enema, including what you need to do to prepare, what happens during the test, and what happens afterwards.
Information and advice about bedbugs, including checking if you have them, how to get rid of them and how to treat bedbug bites.
Read about a group of medicines called beta blockers, including what they're used for, side effects and what to do if you miss a dose or take too much.
A black eye is bruising to the tissue under the skin surrounding your eye.
Read about blood clots, their symptoms, when to get help and how to prevent them.
Find out about blood groups. There are four main blood groups – A, B, AB and O.
Read about finding blood in your semen when you ejaculate, which is usually only temporary and the cause is rarely anything to worry about.
Find out about blood in urine (pee). It's not usually anything serious, but sometimes it can be, so you should get it checked out by a GP.
Find out when to get your blood pressure tested, how the test is done, and what your result means.
NHS information and advice about body dysmorphic disorder (BDD or body dysmorphia), including what the symptoms are and what can help.
Information about boils and carbuncles, which are red, painful lumps on the skin that are usually caused by a bacterial infection.
Botulism is a very rare but life-threatening condition caused by toxins produced by Clostridium botulinum bacteria.
Read more about bowel polyps, which are small growths on the inner lining of the bowel. They are common, affecting 1 in 4 people, and do not usually cause symptoms.
Find out about the symptoms, causes and treatments for Bowen's disease, a very early and easily treatable form of skin cancer.
A brain tumour is a growth of cells in the brain that multiplies in an abnormal, uncontrollable way. Find out about its symptoms and how it's treated.
Read about breast pain and what can cause it. It's usually linked to periods. Other possible causes include injury, certain medicines and infection. Breast pain can also be an early sign of pregnancy.
Find out whether you might be eligible for breast reduction surgery on the NHS and what to do if you think you might qualify.
Read about breath-holding in babies and children, including when to get medical help, what happens during an episode and what to do. Find out about blue breath-holding spells and reflex anoxic seizures.
Find out how to tell if your ankle is broken (fractured), when to get medical advice, and how long it takes to heal.
Find out how to tell if you have a broken arm or wrist, where to get medical help and how long it takes to heal.
A broken collarbone, or fractured clavicle, is a common injury. It usually happens after a fall or a blow to the shoulder.
Find out how to tell if you have a broken finger or thumb, what you should do, and how long it takes to heal.
Read about the signs of a broken leg, what you should do if you think someone has broken their leg, how a broken leg is treated and how long it takes to recover.
Find out about the signs of a broken nose, how to look after your nose at home and when you should seek medical advice.
Read about how long it takes injured ribs to heal, how to look after yourself until you're feeling better, and when you should get medical advice.
Find out about the symptoms of a broken toe, when you should get medical advice, and how to look after it at home.
Find out about bronchitis, including the difference between acute and chronic bronchitis, plus the symptoms, causes, treatment, complications and when to see a GP.
Read about brucellosis, which is a bacterial infection starting in animals that can cause long-lasting flu-like symptoms. It's rare in most developed countries.
Brugada syndrome is a rare but serious condition that can cause the heart to beat dangerously fast.
Blue skin or lips need to be checked urgently in hospital. See a GP if you have blue fingers or toes.
Information for people with vision loss including details of support organisations, plus advice about specialist equipment, home modifications and mobility.
Find out how to relieve back pain, what can cause it, and when to get medical advice.
Bacterial vaginosis (BV) is a common cause of unusual vaginal discharge. BV is not a sexually transmitted infection (STI), but it can increase your risk of getting an STI such as chlamydia.
Find out what causes bad breath (halitosis), how to treat and prevent it, and when to seek medical advice.
Find out what a Baker's cyst is, what causes it, how it's treated and when to see your GP.
Find out what a Bartholin's cyst is, what the symptoms and causes are, and the possible treatment options.
Bedwetting can be worrying and frustrating, but it's common for children to accidentally wet the bed during the night. The problem usually resolves in time.
Read about Behçet's disease, a rare and poorly understood condition in which blood vessels and tissues may become inflamed (swollen).
Read about Bell's palsy, which is a condition that causes temporary weakness or paralysis of the muscles in 1 side of the face.
Information about benign (non-cancerous) brain tumours, including types of tumour, when to see a GP, causes, treatment and recovery.
Understand more about bile duct cancer, its symptoms, when to get medical help, testing and diagnosis, treatment and where to find help and support.
Read about binge eating disorder, which is when a person feels compelled to overeat on a regular basis. Find out about the symptoms, treatments and possible causes.
A biopsy is a medical procedure that involves taking a small sample of body tissue so it can be examined under a microscope.
Bipolar disorder, previously known as manic depression, is a condition that affects your moods, which can swing from one extreme to another.
Find out about birthmarks, including information about 6 of the main types, when to see a GP, and whether or not treatment is needed.
Bladder cancer is where a growth of abnormal tissue, known as a tumour, develops in the bladder lining. In some cases, the tumour spreads into the surrounding muscles.
Read about bladder stones and what causes them. Also, find out when to see your GP and how bladder stones are treated.
Bleeding from the bottom (rectal bleeding) is often seen as small amounts of bright-red blood on toilet paper or pink water in the toilet. Find out when to get medical help if you keep bleeding from your bottom.
Blepharitis is a condition where the edges of the eyelids become red and swollen (inflamed).
Read about blisters, which are fluid-filled bumps under your skin that you can get if your skin is damaged. Find out how to treat blisters yourself, how to avoid getting them, and when to get medical help.
Everything you need to know about blood tests, including why and how they are done, with links to other useful resources.
Find out how to stop yourself blushing and read about the possible causes and treatments.
Primary bone cancer is a rare type of cancer that begins in the bones. Around 550 new cases are diagnosed each year in the UK.
NHS information about bone cysts, including how they're treated and what causes them.
Read about borderline personality disorder. Personality disorders can cause a range of distressing symptoms and patterns of abnormal behaviour.
Read about bowel cancer, a general term for cancer that begins in the large bowel. Bowel cancer is sometimes called colon or rectal cancer.
Information on bowel cancer screening with links to other useful resources.
Read about bowel incontinence, including the symptoms, what causes it and the treatments available.
A brain abscess is a pus-filled swelling in the brain. It's a rare and life-threatening condition, usually caused by infection or a severe head injury.
Find out what a brain aneurysm is, including why they develop, who's affected, how they're treated and how to prevent them.
Brain stem death is where a person no longer has any brain stem functions, and has permanently lost the potential for consciousness and the capacity to breathe.
Read more about a breast abscess – a painful collection of pus that forms in the breast. Most abscesses are caused by a bacterial infection.
Read about breast cancer in women, the most common type of cancer in the UK, including information on symptoms, causes, diagnosis, treatment and prevention.
Read about the symptoms of breast cancer in men, what causes it, how it's treated, and what the outlook is.
Breast screening aims to find breast cancers early. It uses an X-ray test called a mammogram that can spot cancers when they are too small to see or feel.
Find out about breast lumps. They can have a lot of different causes and most are harmless. But always see a GP if you have a lump in your breast or any unusual changes to your breasts.
Bronchiectasis is a long-term condition where the airways of the lungs become abnormally widened, leading to a build-up of excess mucus that can make the lungs more vulnerable to infection.
Bronchiolitis is a common lower respiratory tract infection that affects babies and young children under two years old.
Read about bronchodilators, a medication used to treat asthma and COPD by relaxing the muscles in the lungs and widening the airways (bronchi).
Read about bulimia nervosa, an eating disorder and mental health condition where someone is binge eating, then making themselves vomit or using laxatives to purge the food from their body.
Burns and scalds are damage to the skin caused by heat. Both are treated in the same way.
Bursitis is where a bursa becomes swollen and inflamed. A bursa is a small, fluid-filled sac that acts like a cushion between tendons and bones.
A DEXA scan is a special type of X-ray that measures bone mineral density (BMD). It's also known as a DXA, dual X-ray absorptiometry, a bone density scan or a bone densitometry scan
Read about benign prostate enlargement (BPE), also known as benign prostatic hyperplasia (BPH), which is a common condition in men over 50 years of age.
Bird flu, or avian flu, is an infectious viral illness that spreads among birds. In rare cases, it can affect humans.
Find out about blood transfusions, including when you might need one, how they're carried out and associated risks.
Bunions are bony lumps that form on the side of the feet. Surgery is the only way to get rid of them, but there are things you can do to ease any pain they cause.
Read about biological medicines, which are used to treat some long-term medical conditions, including rheumatoid arthritis, uveitis, Crohn's disease, psoriasis and ankylosing spondylitis.
Bullous pemphigoid is a skin condition that causes a rash and itchy blisters. It usually affects people aged over 70.
Information and advice about how to treat body odour, including when to see a GP if the problem persists.
This guide includes all you need to know about caring for your baby.