Why do head lice make me itch?

Why do I have an itchy scalp?

An itchy scalp can often be a symptom of head lice. However, it is important to rule out other potential causes of an itchy scalp.  So, what else could be making your scalp itchy other than head lice?

DANDRUFF– is a common skin condition that causes visible flakes of dry skin on the scalp. People with dandruff often experience an itchy scalp.  The little white/grey flakes of dry skin means dandruff can often be confused with nits because they are similar in colour and found close to the scalp.  Dandruff is more easily removed from the hair than nits, as nits are glued to the hair shaft.  To stop the itch caused by dandruff there are shampoos you can buy from supermarkets or pharmacies containing ingredients such as coal tar, selenium sulphide, salicyclic acid or zinc pyrithione.¹

ALLERGIC REACTION – if you have an itchy scalp and a rash, you may have a condition called allergic contact dermatitis. This is common among people who dye their hair.³  To get relief from the itch caused by an allergic reaction you must stop using the product that is causing the reaction.³

SCALP PSORIASIS – a condition which causes red patches of skin covered in thick, silvery-white scales that can occur on parts of your scalp or on the whole scalp.⁴ This is a condition that can cause itchiness of the scalp.⁴ To relieve the itch caused by scalp psoriasis, there are medicated shampoos available over the counter at pharmacies or other treatments available on prescription from your GP.⁴

SCALP RINGWORM – a fungal infection affecting the scalp resulting in a red and intensely itchy rash.³  A pharmacist can help with ringworm, they can look at your rash and recommend the best antifungal medicine. This might be a cream, gel or spray depending on where the rash is.⁵ 

HIVES - are red, raised, and very itchy bumps that can form anywhere on the skin, including the scalp.³  Hives rashes usually settle down within a few minutes to a few days.⁶  If the hives do not settle on their own you can talk to a pharmacist about antihistamine tablets that may help relieve the hives.⁶

SCABIES – one of the key symptoms of scabies is intense itching, especially at night.⁷ Scabies   is caused by a tiny bug called the human itch mite and usually start on the hands but can spread anywhere on the body.³ Scabies is very infections, and unlike head lice, everyone needs to be treated in the household regardless of symptoms.⁷   

PSYCHOSOMATIC ITCH – an impulse to scratch when there is no physical cause for the itch.

Why does your head itch with nits?

It is not necessarily nits making your head itch, as nits are technically the empty shells of hatched louse eggs.  It is what comes out of the nit eggs that is making your head itch – the head louse. Head lice are tiny wingless parasites.  A parasite is an organism that takes nourishment from its host.  To survive, head lice need to feed on blood from a human scalp several times a day; without blood a head louse will die within 1-2 days.⁸  It is the feeding habits of the head louse that causes an itchy scalp.⁹  Itching only occurs if the person affected by the head lice become sensitised to the lice saliva, and this sensitisation can take 4 to 6 weeks.⁹ Sensitisation is essentially becoming allergic to the louse saliva. It is not only the saliva of the head louse that can make you itchy, it is also their faeces (poo).¹⁰

Itch is not the most reliable symptom to let you know there is head lice present, especially if it is the first encounter with head lice.⁹ In fact, some people may not even be aware they have head lice as they do not experience the itch and other symptoms.  The only truly reliable way to diagnose head lice is to find a living louse.⁹

Other signs, symptoms or complications of head lice

There can be other clues to let you know you have a head live infestation, particularly if the infestation has went undetected for a long time.

• CRAWLING SENSATION – people often feel a sensation of crawling on the hair or scalp¹¹
• PRURITIC RASH – an itchy rash usually found on the back of the neck and behind the ears, caused by an allergic reaction to louse faeces¹²
• LOSS OF SLEEP – often caused by continuous itching¹²
• EXCORIATED SKIN – caused by continuous scratching¹²
• SKIN INFECTION – caused by scratches becoming infected¹²

How do I treat the itch caused by head lice?

An itch by itself is not a reason to start head lice treatment, you must first confirm an active infestation by detecting living, moving lice.¹⁰ However, if you do find an active head lice infestation and use an over-the-counter treatment, the itch should subside once the head lice have been eliminated.  If after using head lice treatment the itch persists you can speak to your local pharmacist about using an antihistamine or topical steroid.

What treatments are available to kill head lice?

These days it is very rare for a GP to write a prescription for a head lice treatment since so many effective products and methods are available and affordable at local pharmacies.  In fact, some areas of the country have prohibited the prescribing of head lice products.¹³

Choosing a head lice treatment method or medicated application depends on how much time you are willing to spend, how much money you are willing to spend, how many people you need to treat in the household, and the hair type and length of the person being treated.  You can speak to your local pharmacist about choosing an option to suit the needs of your family.  Below are a list of methods or treatments a pharmacist may recommend:

WET COMBING – can be a time consuming method of detecting and removing head lice and has not shown to be as effective as insecticides, especially if the person doing the wet combing is inexperienced.⁹ Wet combing is the methodical combing of hair with a nit comb after the application of liberal amounts of conditioner.  To be successful, wet combing needs to be done on days 1, 5, 9 and 13 to catch any newly hatched head lice. Check again that everyone's hair is free of lice on day 17.¹¹

OVER THE COUNTER TREATMENTS – there are several treatments available in your local pharmacies, online and in supermarkets that can be used to treat and eliminate head lice.  Treatments are available in different formats such as lotions, shampoos, and sprays.¹¹ Some treatments need to be repeated after a week to kill any newly hatched lice.¹¹ 

If you have any unanswered questions about symptoms or treatments for head lice and nits, speak to your pharmacist first.  They are the most accessible healthcare professional equipped to help you with head lice and nits.  We hope our article did not make you itch too much.