As I have emphasised in many of my previous presentations and blogs, fungal skin infection is very common but also recurrent. Untreated skin infection can lead to nail infection. Therefore, for those patients with recurrent tinea, it is important to emphasise that treating (and preventing) it can help reduce subsequent nail infection. Although no study yet has been conducted to prove this point (probably because it would be difficult to design), logic suggests this to be the case. Many patients come into clinic as their nails are just starting to change colour distally as the dermatophytes get under the nail. Inevitably they have the tell-tale signs of tinea pedis elsewhere on their feet. Moreover, studies cite tinea pedis as a significant risk factor for onychomycosis (1, 2).
Whilst it is pretty clear that topical anti-fungal drugs are useful for treating tinea pedis as documented in the Cochrane review of 2002 (3), the evidence for their use in the prevention of nail re-infection is there, albeit through fewer studies. The most recent paper (4) built on previous work (1, 5-7) to try and answer the question – does the regular use of topical antifungal drugs reduce nail re-infection rates following a mycological cure?
The study included 320 patients who were mycologically cured with oral agents (terbinafine or itraconazole) first and then prescribed a topical antifungal agent or nothing at all. The prescribed topical agents were quite diverse ranging from an azole cream (bifonazole), terbinafine spray or a nail lacquer (amorolfine or ciclopirox [not UK approved]). Patients were instructed to apply these just once weekly.
The study concluded the following:
1. Without the use of topical prophylaxis, about 76% of patients experienced recurrence of onychomycosis following cure, compared to 33% of patients using the various topical antifungals during the study period.
2. No one topical agent use in the study appeared to be superior in prevention.
3. Factors which increased the risk of relapse were having multiple toes infected and a family history of fungal nail infection.
So, what should we suggest to our patients about preventing nail and skin re-infection?
Based on the literature cited above, I generally discuss with patients their fungal foot infection problem and emphasize the chronic, recurrent nature. Following treatment, without prevention, it is very likely to return and put them back to square one. Accordingly, as per the literature, I recommend the regular use of a topical antifungal product. My favoured treatment for this is topical terbinafine 1% cream. I generally advise patients to use this once daily for a week, every month. So effectively this is one week on, three weeks off treatment. This should be enough to keep the skin clear of the tell-tale signs of that dry, chalky appearance accentuated in the skin creases and prevent it spreading back to the nails.
Why don’t I recommend clotrimazole? Well, studies have demonstrated that one week of topical treatment to the skin with terbinafine should be sufficient to cure tinea pedis (8), whereas azoles may require 2-4 weeks. So the azoles may not be up to the job in that short time frame. In the summary of terbinafine’s product description (click here), it is noted that in one study of interdigital infection more than 90% of patients with interdigital tinea pedis (athlete's foot) treated with Terbinafine 1% cream for one week showed no mycological evidence of relapse or re-infection by three months after start of treatment (9). This may suggest that a three-monthly preventative regime maybe just as suitable but remains untested for tinea pedis on the soles or elsewhere on the foot.
In addition, for those wanting to be even more vigilant against nail re-infection, the application of amorolfine lacquer 5% to the nails once a fortnight can be efficacious as reported in an Icelandic study (5). Studies to date have not shown any adverse effects whilst using these products in this way.
One final point. Always consider that a fungal infection could be more widespread than anticipated. Typically, with tinea pedis, particularly T rubrum, it will spread to the toenails and the groin, more so in male patients. A proportion of patients will suffer with recurrent tinea cruris and not relate this to their athletes’ foot. Untreated tinea cruris can easily re-infect the foot as the underpants can be a vector for transmission between these two areas. Tactful questioning and advice may help them to connect the two and manage them together. Untreated tinea cruris can undo all the good work on the foot. Also, the same topical creams like terbinafine 1% can be safely used on the groin as well as the foot meaning no additional drugs to be purchased or prescribed.
How to apply antifungal cream
Anti-fungal creams or sprays should be applied clean, dry skin. I always recommend that for a cream this should be enough to cover the whole foot below the ankle, including between the toes. How much cream should a patient use? A simple way to measure out a dose is to ask the patient to squeeze out a strip of cream from the tube along the length of the distal phalanx of their index finger. Depending on their size this roughly 0.4-0.5 of a gram.
The finger tip unit = 0.4-0.5 gram
This is known as the fingertip unit. This should be just enough for one application on one foot. At this dosage a 15g tube should last a fortnight. It should be applied to everywhere on the foot below the “moccasin line” not forgetting the interdigital spaces and flesh of the toes around the nails. For terbinafine, that’s once a day. Patients should apply this one week in four, unless there is evidence sooner of a returning fungal infection.
The Moccasin Line
A topical nail lacquer such as amorolfine can be applied weekly, if additional nail infection prevention is desirable.
References
1. Tosti A, Hay R, Arenas-Guzman R. Patients at risk of onychomycosis--risk factor identification and active prevention. J Eur Acad Dermatol Venereol. 2005;19 Suppl 1:13-6.
2. Scher R, Baran R. Onychomycosis in clinical practice: factors contributing to recurrence. Brit J Dermatol. 2003;149 (Supp 65):5-9.
3. Crawford F, Bell-Syer S, Torgerson D, Young P, Russell I, editors. Topical treatments for fungal infections of the skin and nails of the foot. Oxford: Update Software; 2002.
4. Shemer A, Gupta AK, Kamshov A, Babaev M, Farhi R, Daniel CR, et al. Topical antifungal treatment prevents recurrence of toenail onychomycosis following cure. Dermatologic Therapy. 2017;30(5):e12545-n/a.
5. Sigurgeirsson B, Olafsson J, Steinsson J, Kerrouche N, Sidou F. Efficacy of amorolfine nail lacquer for the prophylaxis of onychomycosis over 3 years. J Eur Acad Dermatol Venereol. 2010;24(8):910-5.
6. Warshaw EM, St Clair KR. Prevention of onychomycosis reinfection for patients with complete cure of all 10 toenails: results of a double-blind, placebo-controlled, pilot study of prophylactic miconazole powder 2%. J Am Acad Dermatol. 2005;53(4):717-20.
7. Tosti A, Elewski BE. Onychomycosis: Practical Approaches to Minimize Relapse and Recurrence. Skin Appendage Disord. 2016;2(1-2):83-7.
8. McClellan KJ, Wiseman LR, Markham A. Terbinafine: An Update of its Use in Superficial Mycoses
Drugs. 1999;58(1):179-202.
9. Electronic Medicines Compendium. Lamisil AT 1% Cream 1999 [cited 2018 30th October]. Available from: https://www.medicines.org.uk/emc/product/6325/smpc.