What is itching?
An itch (pruritus) is a sensation that causes the desire or reflex to scratch. Itching is different to pain in that an itch creates a scratch reflex, whereas pain causes a withdrawal reflex. Itching can be brought on by a wide variety of different stimuli, and several different mechanisms.
The sensation of itch can be reduced by pain. Various painful stimuli, including heat, physical rubbing / scratching, chemical and electrical forms of pain can stop an itch for a period lasting from seconds to minutes, on the painful area and surrounding skin.
Types of itching
Most itches are caused by triggering the itch receptors in the skin from a variety of stimuli, including mechanical, chemical, thermal and electrical stimulation. Itching is never felt in muscle or joints, and is probably only felt in the top two skin layers (the epidermis and the dermis).
Another type of itching is caused by diseases or disorders of the central nervous system or peripheral nervous system. Examples include trauma or irritation to nerves, notalgia paresthetica, brachioradial pruritis, brain tumours, multiple sclerosis and peripheral neuropathy. A neurogenic itch can be brought on by neural damage, usually from the accumulation of opioids.
Lastly, itching is associated with some symptoms of psychiatric disorders such as obsessive-compulsive disorders (as in OCD-related neurotic scratching), tactile hallucinations or delusions of parasitosis.
Causes of itching
Infections and parasites
- Fungal infections such as athlete's foot (tinea) or jock itch.
- Lice (body, hair and head, pubic).
- Mites (rosacea, scabies.
- Hookworm, sandworm.
- Insect bites (mosquito, spider, flea, tick etc).
- Lake itch or swimmer's itch, caused by an immune reaction to water-borne schistosomatidae.
Environmental / toxin / allergen
- Dry skin. This is the most common cause of itching, frequently seen in the winter and also associated with older age, frequent bathing in hot showers or baths, and high-temperature or low-humidity environments.
- Allergic reaction (eg food allergies, poison ivy, oak).
- Scab healing, scar growth and the development of moles, pimples and ingrown hairs from below the epidermis.
- A variety of skin disorders such as urticaria (hives), psoriasis, eczema and many others.
- Thyroid problems.
- Hyperparathyroidism (overactive parathyroid glands).
- Iron deficiency anaemia.
- Varicella (Chickenpox).
- Kidney disease.
- Medications / pharmaceuticals.
- Chloroquine, morphine, various opiates.
Pregnancy can bring on various forms of itching.
Remedies for itching
Anal itch (pruritus ani, anusitis)
Pruritus ani (anusitis) is itchy skin around the anus or exit of the rectum, causing the desire to scratch. In the worst cases, anal itching causes intolerable discomfort accompanied by burning and soreness. Up to 5% of the American population experiences anusitis daily.
Causes of anal itch
- Anal perspiration.
- Residual stool deposits, or the escape of small amounts of stool as a result of incontinence or flatulence.
- Candidiasis (yeast infection). Possibly caused by the use of antibiotics, or reduced immune function from diabetes or HIV infection.
- Anal leakage caused by fistulas, Crohn's disease, or poor digestion.
- Intestinal parasites such as pinworms.
- Anal fissures (tears or cuts on the anal skin).
- Skin tags (abnormal local growth of anal skin).
- Diet. Foods that are not digested well, or that contain irritating chemicals.
- Psoriasis in the anal area.
Triggers that set anusitis off or make it worse.
- Moisture / perspiration.
- Pressure or rubbing caused by clothing and sitting.
Treatments for anal itch
- Treatment should start with measures to reduce irritation to the perianal area, improve digestion, and prevent constipation or diarrhoea. Any other possible causes should be treated.