Devil's claw - also known as grapple plant, wood spider and by its Latin names harpagophytum procumbens or harpagophytum zeyheri - is a herbal medicine traditionally used for the relief of backache, rheumatic or muscular pain and general aches and pains in muscles and joints.
It is also used for relief of the symptoms of digestive disorders, such as bloating and flatulence where there is loss of appetite.
Devil's claw is one of the top eight most popular herbal ingredients in the UK.
The active ingredient is extracted from the root of the plant, a member of the Bignoniaceae family, which is native to deserts of south and south east Africa.
Some devil's claw products are registered with the UK medicines regulator, the Medicines and Healthcare products Regulatory Agency (MHRA), under the Traditional Herbal Registration (THR) scheme. This does not mean the regulator has tested products, which contain it to prove it works or that any claims about it have been verified by clinical studies. However, it does mean that devil's claw has been confirmed as being used as a traditional medicine for at least 30 years - and 15 years in the EU.
Registration also confirms the product manufacturer is meeting established standards of safety and quality.
Some serious side-effects have been reported in patients taking devil's claw, including abnormal heart rhythm and bleeding. Other less serious side-effects are skin rash, stomach upset, diarrhoea, headache and loss of appetite.
There have also been problems documented in the way that devil's claw interacts with some medications: anticoagulants (e.g. aspirin), painkillers (e.g. ibuprofen), heart drugs (e.g. digoxin) and stomach acid drugs (e.g. famotidine).