Your eyes, feet, hair and nails can betray signs of potentially serious illnesses ranging from diabetes and thyroid problems, to liver disease and poor diet.
It is therefore important to check your body regularly and be aware of any early symptoms before checking them out with your doctor.
Spotting these potential illnesses is a question of knowing what telltale signs to look out for. Follow our step-by-step guide to self diagnosis.
Puffy eye lids
'An overactive thyroid is the overproduction of a hormone called thyroxin, which can cause weight loss, anxiety, increased appetite and hyperactivity,' says Tony Weetman, professor of endcrinology at the Northern General Hospital, Sheffield.
Alternatively, bags under the eyes, puffiness of the lids and thinning of the middle of the eyebrows are signs of an underactive thyroid. These symptoms are associated with lethargy, reduced appetite and weight gain.
Natural ways to help boost your thyroid function include eating plenty of iodine-rich food such as sardines or taking kelp supplement.
Ulcers on feet or legs
There are 1.4 million known diabetics in the UK and, if left untreated, the disease can have serious consequences. Most of those are suffering from Type 2 diabetes, which can usually be controlled by diet, exercise and drugs.
Undiagnosed Type 1, or insulin-dependent, diabetes causes the sufferer to fall suddenly and acutely ill as a result of a dangerously high blood sugar level.
'Ulcers start to appear when the blood sugar level is so high it provides a breeding ground for bacteria,' says nurse Simon O'Neill, from the British Diabetic Association.
'When someone is diabetic, the body is less able to produce white blood cells to fight off infection - that's when ulcers start to form and become infected.'
The most common causes of hair loss are pregnancy - which stops one to four months after the birth of a baby - stress and poor nutrition. With most of these, hair loss is temporary and can be helped.
If nutrient levels are low it will be expressed through the hair. Hair follicles rooted in the scalp need to be surrounded by a rich supply of blood to ensure they are sufficiently nourished.
'Hair loss represents low mineral status, specifically lack of zinc, selenium, calcium, sodium and potassium,' says Maria Griffiths of the Institute of Optinum Nutrition.
It can also signify iron-deficiency. Even if you are not anaemic - a reduction in the concentration of haemoglobin or oxygen-carrying constituent of the red blood cells - you may still have low iron stores which can affect hair loss.
Meat provides the best source of iron. Try to eat lean red meats at least twice a week. An alternative is an iron supplement, available from most chemists.
A gynaecological problem known as polycystic ovary syndrome (PCOS) is another reason for hair loss. Women with PCOS have an excess of androgens (male hormones), their ovaries tend to be larger than average, and the ovaries' outer surface have an abnormally large number of small follicles that grows around the ovaries.