What is foam sclerotherapy? Foam sclerotherapy is a common treatment for varicose veins. Performed under ultrasound control, a drug is injected into the veins. This drug destroys the internal lining of the veins and thereby the actual veins themselves die off and gradually disappear. The drug (Sodium Tetradecyl Sulphate) is far more effective if made up with gas into a foam. Although some doctors use foam sclerotherapy as the primary (only) treatment for varicose veins it is not nearly so effective as laser for destroying the larger veins which most patients have underlying their problem. We therefore normally use the more effective laser as primary treatment and only use foam sclerotherapy for a secondary treatment after laser to treat the actual varicose veins rather than their source. This is in line with NICE guidance. The majority of people require both treatments.