What inspires us to cover a topic in Join the Docs with so much fascinating medical information we want to tell you about? Anatomy alone, one of my loves, countless bones, muscles, nerves, arteries, organs.....I could wax lyrical about the scaphoid, one of the tiny wrist bones. Or ear wax. So, Nigel and I wait for the Muse to visit and inspire us.

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Possibly a horrible visual for you, but in this case the inspiration came when taking a shower at a friend’s house. I picked up the shampoo tube and did a double take. Why? Because it contained white tea and aloe. The aloe made sense, a cactus extract believed to soothe inflamed skin; but TEA? I am British and love a cuppa, but have never been inspired to brew a pot and tip it over my head! So, this had me scratching an itch about how things we apply to our skin may cause inflammation and itching, or pruritus as we call it.

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As a linear thinking surgeon and pilot, I like to define and categorise topics. In 1660, German physician Samuel Haffenreffer, described itching as “an uncomfortable sensation that provokes a desire to scratch.” That is rather like saying pain is that sensation that provokes a desire to scream! Itching is, in fact, on the spectrum of pain, and the sensation is carried to the brain by specialised nerve fibres.

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Itching can be provoked either by something in the skin or an external stimulus causing the release of chemicals like histamine from specialised cells which has many effects. Scientists and the pharmaceutical industry have developed pain killers that work in a range of manners, but we do not have similar options with itch killers; antihistamines prevent histamine release and other drugs interfere with nerve conduction, but itching can be troublesome to treat as scratching leads to more histamine release and more itching.

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• Congenital: These are rare problems one is born with such as inborn errors of metabolism where chemical reactions in the body are flawed.
• Topical causes: This is where the provocation is applied directly to the skin becoming inflamed and itchy. Perfumes may inflame passion when detected on the object of one’s desire, but sometimes perfume, cosmetics, washing detergents, and household cleaners cause allergic reactions. Identifying and avoiding the offensive substance is key, but sometimes manufacturers change formulations, so bear this in mind.

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A brush with various plants can lead to temporary, but potent itching; stinging nettles can be transitory, but poison ivy, poison oak or sumac which release a sticky oil, urushiol and this can be enduring. As obnoxious as these may be, they are inconsequential compared to Queensland, Australia’s Dendrocnide moroides, or “gympie-gympie” but more prosaically known as the “suicide plant” whose sting can induce pain that lasts for years. And you thought the crocodiles were a threat!

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Insect bites cause the release of histamine and other chemicals resulting in all the signs of inflammation and itching. For fear of inviting the ire of women reading this, I shall not point out that it is only female mosquitoes who bite.....did I say that out loud? Oops. Other annoying arthropods include bedbugs, lice, scabies, and chiggers, nasty little brutes that cause the most intense irritation.

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Moving to the nether regions, threadworm infestations can cause intense nighttime anal itching when the worms come out to party. They are common among younger children as they are readily passed from one to another if post-toilet hand washing is not thorough.

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Systemic causes: this is where one inhales, eats or drinks an allergen. Food allergies are a major topic of concern and beyond gastrointestinal upset can present with itchy skin. Seafood is often implicated and may be associated with an allergy to various iodine-based contrast agents used in radiologic procedures, so tell your doc if you have this problem. Allergies to peanuts, eggs, milk, and wheat among others are gaining visibility. Originally found in America, and now in Canada, the Lone Star Tick is the vector of a wretched allergic reaction that can include itching. The tick carries alpha-gal, a protein found in mammals other than humans. If bitten by one of these blighters, the immune system mounts a response, such that when one next eats meat, an allergic reaction ensues.

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Several drugs can cause pruritus including a wide range of antibiotics, antifungals, and anticonvulsants. A particular type of itchiness is formication. Derived from the Latin word formica, meaning “ant,” it is the sensation of insects crawling around your skin. It has many causes but may be initiated by taking various drugs, most often, cocaine.

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Dermatitis  is a chronic skin disorder causing itchy, scaly rashes. Diaper rash is one such example but anything inflaming skin can present with this. Sometimes we cannot figure out what the agent was and it settles on its own.

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Dermatographia: In this condition, the slightest pressure on the skin induces an irritating swelling which tends to subside with time and is usually nothing to worry about.

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Eczema is a reactive skin condition worsened by heat. In addition to steamy summer days, or overheated rooms, other things such as fever can raise body temperature and inflame delicate flesh.

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Psoriasi  is an autoimmune disease causing skin redness and irritation, usually in the form of “plaques,” or discs. This can be very itchy and may be associated with arthritic problems, most often in the small joints of fingers or wrist.

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Infections: various diseases, caused by a virus, bacteria or fungus produce itching. I am a fungus fanatic and love every variety of mushrooms. But some fungi are definitely not appealing, causing intense skin complaints – ringworm (despite its name, this is a fungus), candidal vaginal infection, or thrush, and athlete's foot are examples. Such fungal infections can take up residence anywhere in the body and are named for that region. Stick to portobello, chestnut and other mushrooms – much nicer!

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Diet: dietary deficiencies of iron and vitamin D among others produce itching.

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Ageing: as we age, dry and itchy skin becomes more common, possibly due to poorer diets. Chronic diseases, more common in the elderly, can be the source of an itch.

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Liver: if bile flow from liver to gut is blocked by scar tissue, tumour or stone, bile “backs up” leading to jaundice, a yellow itchy complexion. Disease within the liver, like cirrhosis can also cause this, as can structural problems one is born with.

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Kidneys:  as a good Englishman, I like steak and kidney pie, a culinary concept my American friends find baffling. Kidney failure leads to accumulation of toxins and the resultant skin warning signs, including intense pruritus, should be taken seriously

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Thyroid: a low functioning thyroid, the butterfly-shaped organ located in front of the windpipe at the bottom of your neck, can lead to weight gain, hair loss, fatigue and skin problems including dryness and itching.

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Cancer: various cancers, such as lymphoma, as well as drugs used to treat them, can cause itching. Any new, persistent symptom, merits a trip to your medic. Doctors prefer to see a patient and confirm their problem is minor than miss a major disease; a sore throat that is just a sore throat is better than seeing someone present with advanced throat cancer.

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Anaemia: reduction of circulating blood can produce many subtle problems, foreshadowing later and more profound issues like breathlessness; itching is one.

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Pregnancy: children are largely adorable, but once they become teenagers, the word “irritating” comes to mind with some frequency. Maybe as a harbinger of things to come, during pregnancy some women experience itching. If they have pre-existing eczema, pregnancy may worsen symptoms, but it can appear in the absence of other disease states.

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Diabetes mellitus: literally means “sweet urine” due to the presence of excess sugar and it damages every organ as well as causing itching. Keep your weight under control and reduce sugar intake; let the only sweet thing about you be your dreams, not your urine!

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Neurological: nervous system problems may cause errant messages to be sent to the brain, fooling it to perceive false stimuli which patients experience as tingling, pain, burning or itchiness, phenomena known as paresthesia. Examples include multiple sclerosis or shingles following a prior episode of chickenpox.

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Psychological: itching can be a manifestation of mental illnesses like anxiety, obsessive-compulsive disorder, major depression and schizophrenia.

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Treatments:

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Identifying and avoiding the cause is key; then consider applying hypoallergenic moisturisers 3 – 4 times daily, certainly after bathing. Bathtub oils are often suggested, but exercise caution as these make tubs or showers slippery, causing falls. Frequent bathing, or perfumed soaps can be an issue, so limit soap use using a moisturising cleaner instead; alternatively, oatmeal baths sometimes help. If hands are badly affected, petroleum jelly can be applied, then wear cotton gloves. In children with itchy psoriasis, wearing gloves at night helps break the itch-scratch-itch cycle. Also, choose non-scratchy clothing and bed sheets that do not retain heat and humidity.

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Cold compresses sometimes help, either purchase or make your own but be careful about applying ice directly to skin. Using over-the-counter hydrocortisone cream can help but read the label carefully because long term use can lead to skin damage and sensitization. Antihistamines, either over the counter or prescribed, are beneficial, but again, read the label as they can be sedating and should be used with caution. In severe cases, oral steroids are necessary but always follow the doctor’s instructions precisely as this medication must be taken in a specific manner.

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Sometimes, having an itch you want to scratch refers to an intangible element in your life, something you need to do, a conversation you feel compelled to have. It is, in my opinion, always preferable to say what you mean and mean what you say and get it off your chest.

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The above are a small sample of itching causes; many are benign and self-limiting; but if you have a persistent and tangible itch on your chest, and it endures, or disturbs your sleep, scratch the urge to scratch it, and instead, see your doctor.