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If it's not a fungal infection - what is it?

So you may have seen a podiatrist and they've told you that whitey-yellowy area on your toenail is not a fungal infection, or you've been diligently applying an anti-fungal for AGES and nothing's changed. Or - worse still - it's looking even more grim. What the devil is going on?!

Fungal Infection Ok, right, I know I've literally just said that it isn't a fungal infection - but this is worth double checking. Has it been tested? There is a brilliant in-clinic option, more information about that here, or your GP can send a sample of the nail off for testing (MC&S, 6 weeks to receive result, free) or you can have a sample tested privately by PCR (3 days to receive result, costly).

If you have been using the same product for a long time, or you used it, the problem went away and then returned, and the same product did little to nothing, resistance to the anti-fungal agent could be the cause. You could try an alternative anti-fungal (i.e. terbinafine instead of amorolfine; read the label) for a minimum of 8 weeks (this is so that there is enough time for the nail to grow so that you can accurately judge whether the product is working or not, NB: healthy adult nails grow 1mm per month). Or - getting boring I know - you should get the nail tested to determine the causative microbe (read below for more info).

Bacterial Infection Cos if it's not a fungus, it could be a bacterial infection. Bacterial infections can also cause changes in colour, texture, and thickness. Pseudomonas is a pretty common infective agent in bacterial infections, and can affect any part of the body. As with all infections, it is more commonly found in folks with reduced immune defences, such as the elderly or immunocompromised, or in someone who's feet get wet and soggy.

I've seen advice online recommending treatment with bleach. In the UK, to my reckoning, we wouldn't do this. I personally certainly wouldn't recommend it. If someone came into my practice with toenails like this, I would - with consent - trim the nail right back (this would be painless, as the infection here will have lifted the nail from the nail bed - or there may have been a lifting of the nail bed second to trauma that allowed the infection in), gently scrape away that green stuff (it will be slightly sticky in texture - TMI?), cleanse the toe in Clinisept+, dress the toes with inadine, sterile gauze, tubegauze and mefix tape and send the patient away with advice to cleanse the toes at home every other day with either Clinisept+ or saltwater and repeat the inadine dressings. Inadine is a brilliant broad-spectrum anti-bacterial, so I would anticipate this should clear up the bacterial infection. Inadine can technically be left in place for up to 7 days, but I would recommend changing the dressing every other day for hygiene purposes, and to keep an eye on the nail bed. I would then recommend after up to 7 days of inadine dressings, the patient ensures they clean the toes with a little saltwater or Clinisept+ after showering and drying their feet for a further couple of weeks - but they may require longer, or less time if the toenail is infection-free; I would advise on a case-by-case basis. Certainly, antibiotics would not be indicated in this particular type of bacterial infection - though there are certain off-the-shelf antibacterials that I would recommend if the infection was being particularly stubborn to clear. Remember - antibiotics will not clear a fungal nail infection

When are oral antibacterials indicated? If a toe, toes or foot is hot, red, swollen and painful, ± any exudate (read: gunge) this typically represents a bacterial infection and oral antibacterials (e.g. penicillin) may be indicated. It's really important to take a probiotic such as kefir or live yoghurt if you are on a course of oral antibiotics. Antibiotics have a deleterious effect on your gut microflora (microbiome). And what about saltwater bathing - what quantities are we talking here? Well, I'd suggest a tablespoon of table salt in a half-filled washing up bowl of warm water or a heaped teaspoon in a cup, dissolved fully - depending on whether you're just going to cleanse one toe. Method-wise, use a cotton wool or sterile gauze swab; soak the swab and apply to the toe with a little pressure and swipe once away from the body, do not scrub or rub the area; repeat a further one or two times with a fresh swab, or soak both feet for 10 mins or so then gently pat the feet dry, or allow to air dry for a few minutes before applying e.g. a dressing or socks.


Psoriasis is an immune-mediated skin disease which can cause pitting, discolouration and changes in nail texture - which can really closely resemble a fungal nail infection, or the two can work in synchrony. Fun. There is no standardised treatment for psoriatic nails, although there have been some promising results with adalimumab (Humira®) as discussed in Dr. Ivan Bristow's post here. A podiatrist can accurately diagnose and hugely improve the appearance of psoriatic nails.

Eczema Eczema, or atopic dermatitis, is a non-infectious inflammatory skin condition. In the toenails, it can cause nail changes, such as thickening, white-yellow discoloration, and/or brittleness.

Trauma Yes - your toenails can be TRAUMATISED (insert sad face emoji here). This means an injury to the nail plate or bed - and may be something that you recall such as stubbing your toe (ouch), or dropping something on it (also non-ideal) which can cause the nail plate to lift from the nail bed (causing a white or yellow discoloration) - or you could be living in blissful ignorance. A *classic* example is shoes that feel "comfortable", but are actually too tight - so the big toenail rubs on the inside of the toebox, causing repetitive microtrauma which leads to detachment of the nail from the nail bed - which will be represented by a white or yellow patch on the nail. (I've used ballet flats in the image below intentionally).

Ingrown Toenails Ingrowing/ingrown toenails, also known as onychocryptosis, occurs when the border of a toenail grows into the skin. It is most often caused by poor cutting technique, but there is definitely a genetic predisposition and some folks' toenails are just more curly than others - and coupled with either poor footwear, or not fastening shoes properly, or even just sweaty feet (causing friction) this can lead to ingrowing toenails. The condition is typically acutely painful and causes redness and swelling of the affected toe. Left untreated, the nail can pierce the skin allowing a portal for infection. As the wound is moist and the skin swells, this can cause detachment of the nail from the nail bed - which, all together now, can cause a white-yellow discoloured nail.

Fungal nails do not tend to be painful - although they can be if the nail has become particularly thickened and there is pressure on the nail bed. To add further confusion, the toe can be red second to localised tinea pedis (fungal skin infection) - but this would tend to be itchy rather than painful.

Lichen Planus Lichen planus is another inflammatory condition that can cause thinning of the nail plate, longitudinal ridging (onychorrhexis), splitting of the nail at the free edge (opposite to the cuticle), lifting of the nail (onycholysis), hard skin (callus) to form under the nail (subungual hyperkeratosis), red patches around the cuticle, and pterygium (scarring of the nail matrix; in nail anatomy, this is where new nail cells are formed - so injury here means the nails will be irreparably damaged). Again, podiatrists can help to accurately diagnose this condition, advise on self-care and improve the appearance and feel of the skin and nails.

Aging As if getting older wasn't fun enough, your toenails will tend to become thicker, brittle and more yellow as you age. This can, in turn, lead to an increased possibility of fungal toenail infections (as damaged toenails allow a portal for the fungus that is naturally in our environment to take up residence). Reduced circulation to the feet plays a part, and will also make it even more difficult to clear an infection (nail growth slows as we age, particular if the circulation

is poor). On circulation, your 'main' circulation (via your dorsalis pedis and posterior tibial arteries) to your feet can be tickety boo, but if your smaller vessels, which essentially 'feed' your toes are impaired - this will negatively impact nail growth and repair.

How can you tell if your small vessels are not working very well? The feet may be cyanosed (blue or red in colour), mottled, you may be prone to chilblains. Contrary to popular opinion, your feet just 'feeling cold' is not indicative that there's a problem with your circulation.

Tumour Although rare, new discolouration of your toenail - particularly if it's a defined stripe of dark brown from cuticle to tip - could be a nail tumour (cancer). See a podiatrist or your GP, who will be able to refer you for specialist dermatological opinion if indicated. Nutritional Deficiencies Poor nutrition or/or vitamin deficiencies can result in changes in the toenails, including discolouration, brittleness, ridging and spooning. White spots do not represent a calcium deficiency; this is more likely where the nail has been knocked and as the toenails grow so very slowly, this takes a long time to grow out. Iron deficiency and thyroid issues may present in the nails; although, in my experience, this tends to be more obvious in fingernails rather than toenails.

Medication Side Effects Some medications can affect the nails as a side effect, changing their colour, inducing photosensitivity (sensitivity to daylight/UV light) or even affecting the blood supply to the nail unit. Problems are usually cosmetic and resolve with withdrawal of the medication. However, there are some instances of drugs leading to ingrown nails, inflammation, erythema, abscesses/tumours - which can cause functional impairment or pain.

Chemotherapy medication commonly causes nail abnormalities. Plus some anti-infective drugs, (e.g. tetracyclines, quinolones, clofazimine) and photosensitive medications (e.g. psoralens and retinoids), can cause the nail plate to detach from the nail bed after exposure to light (leading to a white-ish or yellow-ish patch on the nail). Off topic, but also interesting, is the correlation between long-term use of beta blockers and pincer nails.

Summary In conclusion - there are clearly MULTIPLE other potential causes for discolouration/brittleness/malformation of your toenails. It's really important you receive a proper diagnosis so that a) you don't waste money and time on a treatment that is never going to work and b) something potentially more sinister isn't missed. Podiatrists - we don't just cut toenails!!

Disclaimer: this content is not intended to replace professional medical advice, diagnosis, and/or treatment. Do not disregard professional medical advice or delay seeking it based on information from this content.


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