Preschool children are at greatest risk of frequent colds, but even healthy adults can expect to have a few colds each year.

Causes- Although more than 100 viruses can cause a common cold, the rhinovirus is the most common culprit, and it's highly contagious.
A cold virus enters your body through your mouth, eyes or nose. The virus can spread through droplets in the air when someone who is sick coughs, sneezes or talks. But it also spreads by hand-to-hand contact with someone who has a cold or by sharing contaminated objects, such as utensils, towels, toys or telephones. If you touch your eyes, nose or mouth after such contact or exposure, you're likely to catch a cold.

Symptoms-Symptoms of a common cold usually appear about one to three days after exposure to a cold-causing virus. Signs and symptoms of a common cold may include:-Runny or stuffy nose,Itchy or sore throat,Cough,Congestion,Slight body aches or a mild headache,Sneezing, Watery eyes, Low-grade fever, Mild fatigue
The discharge from your nose may become thicker and yellow or green in color as a common cold runs its course. What makes a cold different from other viral infections is that you generally won't have a high fever. You're also unlikely to experience significant fatigue from a common cold.

Risk factors--These factors can increase your chances of getting a cold:
Age. Children younger than six are at greatest risk of colds, especially if they spend time in child-care settings.
Weakened immune system. Having a chronic illness or otherwise weakened immune system increases your risk.
Time of year. Both children and adults are more susceptible to colds in fall and winter, but you can get a cold any time.
Smoking. You're more likely to catch a cold and to have more severe colds if you smoke.
Exposure. If you're around many people, such as at school or on an airplane, you're likely to be exposed to viruses that cause colds.
Acute ear infection (otitis media). This occurs when bacteria or viruses enter the space behind the eardrum. Typical signs and symptoms include earaches and, in some cases, a green or yellow discharge from the nose or the return of a fever following a common cold.
Asthma. A cold can trigger an asthma attack.
Acute sinusitis. In adults or children, a common cold that doesn't resolve can lead to inflammation and infection of the sinuses (sinusitis).
Other secondary infections. These include strep throat (streptococcal pharyngitis), pneumonia, and croup or bronchiolitis in children. These infections need to be treated by a doctor.
Homoeopathic remedies are found to be very effective for common cold. Some of the important remedies are given below.
ARSENIC ALBUM 30-Arsenic album is one of the top remedies for common cold. Arsenic alb .is prescribed  when there is a thin watery discharge from the nose and  the discharge leads to a burning sensation and most of the times it is accompanied by sneezing. The person’s condition gets worse in cold air. Being in a warm room can provide some relief to the person.The patient is restless and there is a thirst for water in small quantities at short intervls.

ACONITUM NAPELLUS 30-Aconite should be given in the beginning of cold and this medicine is effective for cold aftera sudden exposure to cold air.It is prescribed when there are   scanty nasal discharge with a stuffy nose and sneezing.  The other accompanying symptoms are restlessness and anxiety. The person may also show an increased thirst for cold water.

GELSEMIUM 1X—Gelsemium is another effective remedy for common cold when cold is accompanied by headache.The patient feels dullness, drowsiness and debility.  The patient also feels feverish. The other symptoms are sneezing, watery nasal discharge. There is a complete absence of thirst for water in most of the cases.

NUX VOMICA 30--Nux Vomica is prescribed   when the nose feels blocked especially during night while during the day, there is a watery discharge from the nose. The cold can be accompanied by extreme chilliness. The patient wants to be warmly wrapped up.

BELLADONNA 30-Belladonna is prescribed for common  cold when pain in throat occurs along with cold. The pain in throat gets worse when you swallow anything. The throat is inflamed and dry. There may  also bouts of cough, along with a headache. Binding the head provides little relief from the headache.

ALLIUM CEPA 30- Allium Cepa is an effective  Homeopathic remedy for a running nose with excessive watery discharge, along with sneezing and headache. The nasal discharge is irritating and burning in character. The patient feels somewhat better in open air. There may be cough with hedache.

ARUM TRIPHYLLUM 30- Arum Triphyllumis  prescribed when the discharge from nose is mostly of an acrid and excoriating type, with a sharp unpleasant smell and feeling.Theptient feels the nose blocked. There is pain and irritation  in the nostrils .Must breathe through the mouth.  Discharge may be bloody

BRYONIA ALB. 30-Bryonia Alba is effective when there is cold and headache.   There is mostly an increased thirst for water.

HEPAR SULPH 30- Heparsulph is prescribed when the nose is blocked , which is worse in cold air. There is  profuse discharge in stuffy colds. Two or three doses are generally sufficient for the purpose. Sneezes every time he goes in the cold dry wind . Nostrils ulcerated. There is cough which is loose and rattling along with cold.

SABADILLA 30-Sabadilla is prescribed when  there is excessive sneezing with a constant running nose. Coryza with spasmodic sneezing. Severe frontal pains, redness and watering of eyes, sore throat beginning left side and tough mucus. Symptoms betterfrom  hot food and hot drinks. Worse cold and cold drinks. No thrist

EUPATORIUM PERFORLIATUM 30-Eupatorium per. Is effective when  have a cold with severe bodyache and muscle soreness of the entire body.
DULCAMARA 30- In Dulcamara the cold is profuse during rain or when the days are hot and nights are cold. There is total blockage of nose without any discharge after cold air exposure.Coryza in new born babies.

SAMBUCUS NIGRA 30-Sambucus is prescribed  when there is extreme dryness and stoppage or blockage of nose mainly during night. The person wakes up at night from sleep due to suffocation as a result of nasal blockage.Coryza and snuffles of infants.

AMMONIUM CARB.30--- Ammonium Carb is prescribed  when the nose is stuffed up completely with the inability to breathe through the nose. The person keeps the mouth open so as to breathe.Discharge of sharp burning  water. Stopage of nose at night.Coryza  of long standing

QUILLAYA SAP.  30—Quillaya is very effective for cold and if given early in the beginning of coryza , it stops the further development of cold, sore throat, dryness of throat  and cough with difficult

SAPONARIA  10M—Saponariabreaks up the cold, coryza and sore  throat . The patient behaves as if drunk.

SOLANUM NIGRUM  30- Solanumnigrum is prescribed for acute coryza , watery discharge from the right nostril, left stopped up, with a chilly sensation alternating with heat.

TRITICUM REP  30—It is an excellent remedy for coryza when the patient blows his nose constantly even when the discharge does not come on each occasion .