Cryotherapy

What is cryotherapy, and how does it work?

Cryotherapy (also called cryosurgery or freezing) uses extreme cold to destroy small, superficial skin lesions without the need for surgery¹. The usual cold source is liquid nitrogen, at -196°C, applied for a few seconds at a time¹.

Freezing kills cells straight away, and then keeps damaging them over the following days². For warts, the localised frostbite is also thought to stimulate your immune system to fight the wart virus³.

It treats the lesion that's there. It doesn't stop new ones developing in future⁴. Cryotherapy should only be given by appropriately trained staff³.

What is cryotherapy used for, and how well does it work?

Freezing is used for viral warts and verrucas (plantar warts), sun spots (actinic or solar keratoses), seborrhoeic keratoses (harmless warty growths), molluscum contagiosum, skin tags, genital warts and Bowen's disease, an early skin cancer³⁴. How well it works depends on the lesion.

• Sun spots: the strongest case. It's rated the most effective and commonly used first-line treatment aimed at individual sun spots⁵. It also cleared more spots than a dummy treatment on the body outside the face and scalp, though confidence in that result is low⁶.
• Common warts: mixed. Cure rates vary with the method, the type of wart and the person⁵, though freezing did better than some other methods⁷.
• Plantar warts: less convincing. The average cure rate is low⁸.
• Plane warts (flat warts): freezing is best avoided, as they often clear on their own⁹.

Is cryotherapy right for me?

It suits selected lesions, once a trained practitioner has judged it suitable for you³. The lesion needs a diagnosis first. Anything with an unusual history or look, or a wart that bleeds or changes, could be something more serious and needs assessment before freezing⁹. Sun spots need checking for early skin cancer first².

For young children, freezing is painful and rarely tolerated under about 7, so it's worth discussing alternatives first¹⁰. It's also described as best suited to light skin and to areas with little hair¹¹. For genital warts during pregnancy, freezing is one option⁷.

What happens during cryotherapy?

Liquid nitrogen is sprayed onto the lesion, or dabbed on with a cotton-tipped swab, usually without local anaesthetic⁴. It's applied from a few seconds up to about 10–20 seconds, until the lesion freezes and turns white, sometimes with a second freeze¹². The skin is then left to warm up¹.

Afterwards the area usually turns red. A scab may form and drop off over 1–2 weeks⁴.

Warts are normally frozen again every 1–3 weeks, and about 70% improve after 3–4 sessions¹³. The full effect can take about 4 weeks to show, and if anything remains after that, you may need more treatment¹². The best freeze time and gap between sessions isn't clear yet, so your practitioner will decide what suits the lesion¹⁴.

What are the risks and side effects?

Stinging, pain, redness, swelling and a blister are common, and are a normal response to freezing³. Less often, freezing can leave a small scar, skin that ends up lighter or darker than the skin around it (this may be permanent), or an infection¹. Healing can be slow, and the wart can come back¹⁴. Deeper freezes take longer to heal².

How does it compare with other options?

For warts, freezing is usually used when other treatments haven't worked, as it can be painful, can scar and may not work¹⁰. For plantar warts in particular, some antiviral, injected and gel treatments did better than freezing¹⁴, so it's reasonable to ask about them.

For sun spots, adding a cream or gel to freezing seems to clear more than freezing alone¹⁵. If you have several sun spots, ask whether treating the whole affected area suits you better than freezing single spots¹⁵. On the head and neck, some creams and light-based treatments came out as most beneficial, though they often cause more side effects early on¹⁶.