Find out about prosopagnosia (an inability to recognise faces), including how the condition can affect a person's everyday life, plus details about commonly used coping strategies.
Panic disorder is where you keep having panic attacks, often for no obvious reason. Includes symptoms, treatments and self-help tips.
Find out about Patau's syndrome, also known as trisomy 13, a serious genetic disorder where a baby has an extra copy of chromosome 13.
Peak flow is a simple measurement of how quickly you can blow air out of your lungs. Read about why and how it's measured.
Pelvic pain is felt below your bellybutton. It may come on suddenly and severely, or could be mild and last for months. See your GP as soon as possible.
Read about penile cancer, a rare type of cancer that mostly affects the skin of the penis. Find out about possible causes and treatments.
Read about period pain, including symptoms, when to see your GP, causes, diagnosing underlying conditions, and treatment.
Find out about periods, including when they usually start and finish, sanitary products, PMS, getting pregnant, and changes to your periods.
Find out more about persistent trophoblastic disease and choriocarcinoma, part of a very rare group of tumours called gestational trophoblastic tumours (GTTs).
NHS information about personality disorders, including the main symptoms and treatments.
Find out about positron emission tomography (PET) scans and how these three-dimensional images of the inside of the body can be used.
Read about phaeochromocytoma, a rare tumour of the adrenal glands, which sit above the kidneys. They're usually benign (non-cancerous), although some are cancerous.
Find out about phenylketonuria (PKU), a rare genetic condition that's present from birth (congenital), where the body is unable to break down phenylalanine.
NHS.UK information on phlebitis and superficial thrombophlebitis, with links to other useful resources.
Find out when a phosphate test may be needed and what it's used for.
Find out what photodynamic therapy (PDT) involves, when it's used and the risks you should be aware of.
Read about pins and needles (paraesthesia), a pricking, burning, tingling or numbing sensation that's usually felt in the arms, legs, hands or feet.
Find out about faulty PIP breast implants, including why they are banned, and the latest safety information on removal and replacement.
Read about pityriasis rosea, which is a relatively common skin condition that causes raised, red scaly patches on the body.
Pityriasis versicolor, sometimes called tinea versicolor, is a common condition that causes small patches of skin to become scaly and discoloured.
Read about why some babies develop a slightly flattened head, what can be done about it, and how long it will take to improve.
Read more about pleurisy, which is inflammation of the tissue between the lungs and ribcage (pleura). The most common symptom is a sharp chest pain when you breathe.
Read about polio, including what the symptoms are, how it's spread, where it's found and the polio vaccination.
Find out about polyhydramnios (too much amniotic fluid), including what it means for you, your pregnancy and your baby.
Polymorphic light eruption is a fairly common skin rash triggered by exposure to sunlight or artificial ultraviolet light. It lasts for up to 2 weeks, healing without scarring.
Read about pompholyx, a type of eczema that causes tiny blisters to erupt across the fingers and palms of the hands. Find out what triggers it and how it's treated.
Postmenopausal bleeding is vaginal bleeding that happens at least 12 months after your periods have stopped.
A post-mortem, also known as an autopsy, is the examination of a body after death. The aim of a post-mortem is to determine the cause of death.
Information on postpartum psychosis (psychosis after childbirth), with links to other useful resources.
Find out about postural tachycardia syndrome (PoTS), an abnormal increase in heart rate that occurs after sitting up or standing.
Find out why and when a potassium test may be needed.
Cancer is not usually inherited, but some types – mainly breast, ovarian, colorectal and prostate cancer – can be strongly influenced by genes and can run in families.
Probiotics are thought to help restore the natural balance of bacteria in your gut when it's been disrupted by an illness or treatment. There's some evidence that probiotics may be helpful in some cases, but there's little evidence to support many health claims made about them.
If you or someone you care for struggles to swallow pills, you should discuss it with a doctor or pharmacist.
Prostate problems are common in men, particularly in those over 50 years of age.
Prostatitis is a condition where the prostate gland becomes swollen. It can come on suddenly and be severe (acute) or come and go over several months (chronic). Read how it is treated.
Find out about psoriatic arthritis, including the symptoms and when to get medical advice. Also, information about causes, diagnosis, treatment and managing related conditions.
Read about the difference between psychiatry and psychology, and find out about the conditions psychiatrists may treat, how to get an appointment, and what your appointments may involve.
Find out about pubic lice, including what they look like, how you get them, symptoms, when to seek medical advice, treatment and possible complications.
Find out about pudendal neuralgia, including what the symptoms are, what can cause it, and how it can be treated.
Read about pyoderma gangrenosum, a rare skin condition that causes painful ulcers. It's usually treatable but may take some time to heal and could leave some scarring.
Find out what a pacemaker is, how it works, why you might need it, and how it's implanted.
Find out about Paget's disease of bone, a condition where the normal cycle of bone renewal and repair is disrupted.
Find out about Paget's disease of the nipple (Paget's disease of the breast). It's a rare condition where eczema-like changes occur in the the skin of the nipple and areola.
Find out about pancreas transplants, why they're carried out, what they involve, and the potential risks.
Understand more about what pancreatic cancer is.
Read about paralysis, including symptoms, causes and treatments.
Read about Parkinson's disease, a condition in which parts of the brain become progressively damaged over many years.
Pelvic inflammatory disease (PID) is an infection of the female upper genital tract, including the womb, fallopian tubes and ovaries.
Pelvic organ prolapse (POP) is bulging of 1 or more of the pelvic organs into the vagina.
Read about pemphigus vulgaris (PV), a rare and serious condition that causes painful blisters to develop on the skin and inside the mouth.
Find out about a perforated (burst) eardrum, including what the symptoms are, what to do if you think you have it, and how it can be treated.
Find out about pericarditis, which is swelling of the pericardium (the fluid-filled sac that surrounds your heart).
Read about peripheral arterial disease (PAD), a common condition in which a build-up of fatty deposits in the arteries restricts blood supply to leg muscles.
Read about peripheral neuropathy, a term for a group of conditions in which the peripheral nervous system is damaged.
Read about peritonitis, which is inflammation of the thin layer of tissue that lines the inside of your abdomen (tummy) called the peritoneum.
A phobia is an overwhelming fear of an object, place, situation, feeling or animal.
Read about physiotherapy, including why it's used, what it involves and how you can access it on the NHS or privately.
Piles are lumps that can appear inside and around your bottom (anus). Most piles go away within a few days without treatment. There are things you can do to ease any pain and discomfort.
Read about pilonidal sinus, which is a small hole or "tunnel" in the skin. It usually develops at the top of the cleft of the buttocks, where the buttocks separate.
Read NHS information about plastic surgery, which is a type of surgery that repairs and reconstructs missing or damaged tissue and skin.
Read about pneumonia, including symptoms, causes, who's at risk, treatment and possible complications. Also find out how you can prevent getting pneumonia.
Read about the signs and symptoms of poisoning and find out what to do if you think someone has been poisoned.
Read about polycystic ovary syndrome (PCOS), a common condition that affects how a woman's ovaries work.
Read about the symptoms and treatment of a blood disorder called polycythaemia, or erythrocytosis, which means having a high concentration of red blood cells in your blood.
Find out about polymyalgia rheumatica (PMR), a condition that causes pain, stiffness and inflammation in the muscles around the shoulders, neck and hips.
Read about post-herpetic neuralgia, which is persistent nerve pain at the site of a previous episode of shingles.
Postnatal depression is a type of depression that many parents experience after having a baby. It's a common problem, affecting more than 1 in every 10 women within a year of giving birth.
Post-polio syndrome is a poorly understood condition that can affect people who have had polio in the past. Polio is a viral infection that used to be common in the UK, but is rare nowadays.
Post-traumatic stress disorder (PTSD) is an anxiety disorder caused by very stressful, frightening or distressing events.
Find out about Prader-Willi syndrome (PWS), which is a rare genetic condition that causes a wide range of physical symptoms, learning difficulties and behavioral problems.
Pre-eclampsia is a condition that affects some pregnant women, usually during the second half of pregnancy (from around 20 weeks) or soon after their baby is delivered.
Read more about premenstrual syndrome (PMS), which is the name for the symptoms women can experience in the weeks before their period.
Pressure ulcers, sometimes known as bedsores or pressure sores, are an injury that affects areas of the skin and underlying tissue.
Read about priapism, a persistent, often painful erection. If it lasts for more than 2 hours, go to A&E to prevent permanent damage.
Find out about primary biliary cholangitis (primary biliary cirrhosis), which is a type of long-term liver disease where the bile ducts in the liver become damaged.
Progressive supranuclear palsy (PSP) is a rare and progressive condition that can cause problems with balance, movement, vision, speech and swallowing.
Prostate cancer is the most common cancer in men in the UK, with over 40,000 new cases diagnosed every year.
Psoriasis is a skin condition that causes red, flaky, crusty patches of skin covered with silvery scales.
Read about psychosis, a mental health problem that causes people to perceive or interpret things differently from those around them.
Read more about a pulmonary embolism, which is a blocked blood vessel in your lungs. It can be life-threatening if not treated quickly.
Pulmonary hypertension is high blood pressure in the blood vessels that supply the lungs. It's a serious condition that can damage the right side of the heart.
Plantar fasciitis is where you have pain on the bottom of your foot, around your heel and arch. You can usually ease the pain yourself, but see a GP if the pain does not improve within 2 weeks.