A patented self-heating solution called LavaGel that contains natural minerals, algae and sea kelp is placed within the clam shells. When combined with salt water, the gel generates heat for up to an hour-long massage.

Therapists then use one or two shells to deliver continuous heat to their client, without losing contact during the treatment, while the shells emit calcium ions when heated.

Sourced from the Philippines, the shells are a part of the everyday Filipino diet, and were previously regarded as waste. The shells are portable, eco-friendly and don't require a steam heater or any other external equipment.

Supplied by the US-based Spa Revolutions company, whose portfolio of products includes a wide range of other self-heated tools for hand, foot, body, and massage care, Lava Shells are distributed in the UK by Shared Beauty Secrets.

Lava Shells have recently launched at The Grove, Hertfordshire, UK; The Spa at The CityPoint Club in London, UK, and the Bali Leha Spa on Necker Island.