Homeopathy requires clear & strong symptoms for effective treatment. A well-chosen remedy can then alleviate symptoms quickly and effectively.
Aconite works well for a cold that starts with a sudden fever after exposure to cold. The person will feel anxious and fearful.
Belladonna is the remedy when symptoms come on suddenly and intensely, fever is high, face is flushed, little thirst.
Ferrum phos can help at the start of a cold with typical runny nose, sore throat. A dose in 6C can be taken 3 times a day on the first day of the cold.