Do you feel like there are insects crawling on your skin or something on your face that's not actually there? DR SCURR reveals the disturbing condition - with no obvious trigger - that's to blame

I have suffered with a 'tactile hallucination' for many years. It feels as if there is something on my face – like a moving liquid. My GP has prescribed amitriptyline before bed to aid sleep but is there anything else that might help? Carol Mills, Bognor Regis, W. Sussex. Dr Martin Scurr replies: Tactile hallucinations are false sensations that can be deeply distracting and disturbing. While I describe them as 'false', they are not imagined – they feel very real to the person affected, but there is no obvious trigger. A common symptom is a sense of something being on, or in, the body – such as insects crawling on the skin, a feeling of permanent wetness on the face or even the sensation of having walked through a cobweb. The explanation is that the brain is misfiring in the regions that process touch sensations – nerve messages between the body and head and the brain. It's rare to find an underlying cause for this, although some neurological disorders, such as Parkinson's disease, epilepsy and even Alzheimer's, can trigger tactile hallucinations, due to changes in brain structure and chemistry. So, too, can certain medications including some antidepressants, anti-epilepsy drugs and the beta-blocker propranolol – widely used to treat high blood pressure. A common symptom of tactile hallucinations is a sense of something being on, or in, the body – such as insects crawling on the skin or even the sensation of having walked through a cobweb In some patients, there may be an underlying mental health problem, particularly those with a psychotic element (e.g. schizophrenia or bipolar disorder). One problem is that some people affected in this way scratch or pick at the skin, causing damage or infection. Reassuringly, you've been prescribed an effective treatment: amitriptyline – a type of antidepressant (called a tricyclic), it helps in tactile hallucination by altering how the central nervous system processes touch signals. I know of no other more suitable medications, so recommend you carry on taking it as it will be perfectly safe at a low dose. Alternatively, you may wish to book a session with a skilled acupuncturist. While I am not aware of evidence to show it's effective, some of my patients have reported it helped them. I am in good general health but have swollen ankles that cause discomfort. My daughter – a nurse – thinks it may be due to my blood pressure medication, amlodipine. Should I ask to be switched to something else? John Jefferis, Wisbech, Cambs. Dr Martin Scurr replies: Your daughter is correct, ankle oedema – or swelling – is a known side effect of amlodipine. This is because it dilates tiny arteries (blood vessels that carry blood away from the heart and around the body) to ease the pressure in them, but it doesn't dilate the veins (which carry the blood back to the heart). This can lead to a build-up of blood, which then leaks into surrounding tissues – causing swelling. However, I'm not convinced switching to another blood pressure drug is wise. Some of the alternatives, such as diltiazem and verapamil, can also cause ankle oedema – and if your current regimen is providing good blood pressure control, it might be better not to meddle with it. Perhaps suggest to your GP a small experiment – reducing your amlodipine dose to 5mg, to see if there is an improvement in the ankle swelling. Meanwhile, wearing compression stockings (which help to propel blood back up through the veins in the legs) is definitely worth trying. But it's vital that they are of the right grade of elasticity and correctly fitted. A good pharmacist can advise you on this, but below knee British Standard Class 2, medium compression (18-24mm/hg – the amount of pressure the sock will exert at the ankle), should be the right size for you.