Flu is a highly contagious viral illness that tends to occur in epidemics during the winter. It is spread by coughs and sneezes of infected people and also by direct contact with contaminated articles such as handkerchiefs.

Most people suffer from occasional forgetfulness, especially in later life when slower brain processing may make it harder for them to store and remember information. However, absentmindedness is not an inevitable part of aging, nor is it confined to the elderly.

Panic attacks are episodes of intense fear with unpleasant physical symptoms that usually occur without any outside threat being present. You may be short of breath or breathe rapidly (hyperventilate) and suffer from sweating, dizziness, nausea, numbness, chest pains, or palpitations. Attacks may be linked to anxiety, stress, depression, a phobia (such as fear of flying), or to taking stimulants or drugs, but symptoms can develop for no apparent reason. Although the attacks usually pass quickly, fear of having them can interfere with normal life.

Most people have occasional low moods, but if you are depressed these become persistent. You may feel tearful and low, particularly in the morning; lack energy and confidence; and find it hard to concentrate or make decisions. Sleep problems and loss of sex drive and appetite are common. Depression is often a reaction to a life event such as bereavement, or it may have no obvious cause. Lack of sunlight in winter makes some people feel sad, and 1 woman in 10 has depression after childbirth.

When you are under stress, your muscles tighten, your heart beats faster, your breathing becomes rapid and shallow, and your brain becomes more alert. In small doses, stress can improve your performance in situations such as sport or work, but if excessive or prolonged it can harm your health. You may suffer poor appetite, headaches, migraine, difficulty sleeping, and increased susceptibility to infections.

Dizzy spells and feeling faint are common problems. Causes include low blood sugar, drinking too much alcohol, or simply getting up too quickly. Feeling faint may also be due to emotional shock or panic, or may occur in pregnancy. An occasional attack is rarely a cause for concern, but sometimes the problem is due to an underlying condition or to certain drugs.

Jet lag is a collection of symptoms that occur while your body clock adjusts to a new time zone when you travel. Until you get used to the local time, you may feel disoriented and tired during the day and have difficulty sleeping at the new night-time. You may also experience poor concentration, loss of appetite, and diarrhoea or constipation. Most people begin to feel the effects of jet lag only after crossing three or more time zones.

Many people have difficulty sleeping, either because they find it hard to get to sleep at night or because they wake early and cannot get back to sleep. Adults need 7-8 hours of sleep, on average, but people need less as they get older, and elderly people may need as little as 5-6 hours. An occasional sleepless night won't do you any harm, although you may feel tired the next day.

A hangover is usually the result of drinking too much alcohol, but some people have symptoms after just a small amount of alcohol. The cause is a combination of the dehydrating effects of alcohol and adverse reactions to chemical additives in drinks, particularly dark-coloured drinks such as red wine, port, brandy, and sherry.

Everyone feels tired after physical exertion or long periods of hard work. A good night's sleep usually solves the problem, but sometimes tiredness seems to drag on for days, and can interfere with your daily activities.

Itching is often a minor problem, but continual scratching may damage your skin and make the problem worse. A small area of itching may be caused by an insect bite or occur with a rash as a reaction to plants, metals, chemicals, or cosmetics.

Almost everyone sweats more than usual when exercising or in hot weather, but some people generally sweat too much. Excessive sweating is common in adolescence but can continue throughout life. It can cause body odour and affect work and social relationships. People who sweat excessively are also more prone to fungal skin infections.

In a fever, your body temperature remains persistently above the normal level of 37°C (98.6°F). A fever is one way in which the body responds to infection, so it is likely to result from a viral illness such as flu, or a throat, chest, or urinary infection. It can also be due to other minor ailments like sunburn, or reactions to drugs. At first you feel warm; if your temperature goes on rising, you feel chilled and shivery, then as it drops you feel hot and flushed. You may become dehydrated if the fever persists.