Guinea pigs don't need to be vaccinated or wormed. Common problems include:
Mange is a tiny parasite that lives in the skin. It is characterized by dry, scaly skin, open wounds and scratching. It is treated with a spot-on preparation.
Most of the time, diarrhoea is caused by eating spoiled/mouldy hay or vegetables, too much fruit or sudden food changes. Probiotics or antibiotics are used as cure.
Not eating for more than 24 hours can be dangerous. If your guinea pig does this, they must be seen immediately to determine the cause and to start treatment.
Their nails can grow surprisingly fast and are often curved. Some guinea pigs need regular nail clips.