5 Fungal Infection Mistakes You're Probably Making

Sep 19

9 min read

Updated: Sep 29

中文摘要在文末

Usual caveat: not a lecture. Most people who come to me with a fungal infection that won't go away have been doing something reasonable — it just wasn't quite the right reasonable thing.

Here are the five I see most, and then a case that took me three visits to solve, which I include partly because it shows how easily I can miss things too.

1. Buying a combination steroid-antifungal cream

I've written a whole article about this, so briefly.

These creams pair a steroid with an antifungal, sometimes with an antibiotic. The logic — cover both possibilities when you're not sure — sounds sensible and mostly isn't.

If it's fungal, the antifungal works while the steroid suppresses the immune response that was containing the infection.So it improves for a few days, then comes back worse. And the steroid strips away the features that would have identified it as fungal, so by the time someone examines it properly, the evidence has been degraded.

My rule: if you're not sure, use one thing at a time. Not for efficacy — to preserve your ability to interpret what happens next.

I use combination creams in roughly one percent of cases, and only when I already know what I'm treating.

2. Stopping the moment it looks clear

This is the biggest one, and it's the reason for most of the recurrences I see.

Fungal organisms are resilient. I use that word deliberately with patients. They persist in skin that looks completely normal, and the visible clearing happens well before the actual clearing does.

So my standard instruction: once it looks completely clear, keep applying the treatment for another one to two weeks.

I know that feels wasteful. The rash is gone. But that extra week or two is the cheapest insurance in dermatology, and skipping it is why people end up treating the same infection four times over two years.

I'll message you afterwards to check you've actually done it — not to nag, but because I know exactly how quickly "it's gone" turns into a tube going back in the drawer.

3. Treating only the visible patch

Two versions of this.

The edge is the active part. In a spreading fungal infection, the advancing border is where the organism is actually working. The centre often looks calmer. So people apply cream to the obvious middle and skip the outer rim — which is the part that matters most. Treat the whole patch and extend beyond the visible edge.

And treat the other sites. Fungal infections travel. Athlete's foot spreads to nails, and to the groin — often via the towel, or by pulling underwear on over feet that are already infected. If you have a groin infection, I'll look at your feet, and I'd suggest treating both even if one seems trivial. Otherwise you clear one and get reinfected from the other, indefinitely.

4. Ignoring the reservoirs

Your skin isn't the only thing carrying this.

Shoes. If you've had a foot infection, the shoes probably still have it. My honest advice: if they're not expensive or precious, throw them out. If they're worth keeping, treat them — with proper advice from a shoe shop, so you don't ruin them in the attempt. People treat their feet diligently for a month and then put them back into the source every morning.

Shared showers. Gyms, changing rooms, communal bathrooms. Wear sandals. These are high-risk areas for fungal infections and for several other things too. Never barefoot.

Towels and bed linen. Change weekly, and don't share towels. This is how it moves between family members, and it's why I sometimes end up treating a household rather than a person.

5. Assuming pets are harmless

Fungal infections from animals are common here, particularly from cats, and especially strays.

The distribution often gives it away: shins and both hands. That pattern exists because animals are low to the ground — so they contact your lower legs — and because people pick them up, which involves the hands.

Two other things worth knowing.

Animal-associated fungal infections frequently come with a bacterial infection alongside them. So I have a lower threshold for adding an antibiotic in these cases, and there's a specific reason for it that I'll explain in the case below.

Keep pets off beds and pillows. Fur stays in bedding for a long time. And it isn't only a skin issue — you're breathing it in as well.

Now, on stray cats specifically. I'm not going to tell you to stop feeding them. That matters to a lot of people here, for reasons that go well beyond the practical, and it isn't my place. What I'd ask is:

Cover your legs. Long trousers and proper shoes rather than shorts and sandals.
Don't handle them. Feeding doesn't require picking them up.
Wash your hands and forearms afterwards.
Change out of the clothes you fed them in rather than sitting around in them.

That preserves the thing you're doing and removes most of the risk. My patient below wasn't harmed by feeding cats. She was harmed by bare shins, sandals, and cuddling.

The case that took me three visits

A woman in her twenties came in with what looked like textbook ringworm. Classic presentation. I was her third doctor — she'd been given antifungal treatment elsewhere, and it either hadn't worked or had worked initially and then recurred.

I did the usual. KOH microscopy came back positive — fungal elements clearly visible. So I had my diagnosis confirmed, and I concluded the previous failures were about treatment not being applied properly or for long enough. Reasonable. I gave topical and oral treatment together and arranged review.

At review, the lesion had changed character. It looked angrier. Less itchy, less scaly — but now infected, with yellow crusting.

I was confused. That's not what successful antifungal treatment looks like.

So I went digging in the history again. No cats at home. But — and this came out only on further questioning — she liked to feed the stray cats in the back alley behind her house. In shorts and sandals.

That explained the source.

And it explained the yellow crusting too. Animal-associated fungal infections usually carry bacteria alongside them. Once the antifungal treatment cleared the fungus, the bacteria no longer had competition on the skin — so they flourished. The infection getting angrier wasn't a treatment failure. It was a consequence of the treatment working.

So I started both antifungal and antibiotic treatment, and arranged review.

It improved. Then it got worse again — despite no change in medication.

More history. She was still going to feed the cats occasionally. Not defiantly — she just hadn't connected my advice to something that felt so ordinary and so kind.

We talked about it again, properly. Once the exposure genuinely stopped, the lesion came under control and eventually cleared completely, leaving some post-inflammatory pigmentation which I told her would resolve over months.

The lesson I took from this was about myself, not her.

I should have asked about animal contact earlier and in more ways — "do you have pets" is not the same question as "do you have contact with any animals." And I should have revisited it at each review rather than assuming that advice given once had landed. It hadn't, because to her, feeding a stray in the alley wasn't "contact with animals." It was a nice thing she did on the way to the bins.

So now I ask repeatedly, and I ask differently each time.

The point for you: cats are cute and they're not harmful — right up until your skin barrier is broken. And the detail you think is too small or too obviously innocent to mention is very often the one that solves it.

And one thing that isn't a mistake

Getting a fungal infection doesn't mean you're unclean. This comes up constantly, usually unspoken, and it stops people seeking treatment.

These organisms are everywhere. Some of them live on normal human skin permanently. In a hot, humid climate with year-round sweating, exposure is unavoidable and infection is common. It has very little to do with how carefully you wash — and as I mention in the nail article, over-scrubbing damages your barrier, which makes things easier rather than harder for the organism.

Simple fungal infections are completely curable. Not managed like eczema. Not maintained like melasma. Genuinely cleared — as long as you finish the course properly and deal with whatever exposed you.

You should see improvement in about a week, and I'll usually review at two weeks. Don't lose sleep over this one.

Klinik Dr Tan (Skin & Acne), Lot 27, Ground Floor, Block D, Lintas Square, Kota Kinabalu. WhatsApp 017-234 7328. Appointments preferred — and bring everything you've applied to it.

Book a consultation with Dr. Tan — Book Online or WhatsApp 017-234 7328.

简要说明

我是陈医生，亚庇 Lintas Square 的 Klinik Dr Tan（皮肤与暗疮）。

1. 买类固醇＋抗真菌的复方药膏

「不确定就两边都涵盖」听起来合理，多数时候不是。如果是真菌，抗真菌成分在工作，但类固醇抑制了正在压制感染的免疫反应——好几天，然后更糟；而且它抹去了能辨认真菌的特征，等到有人认真检查时，证据已被破坏。原则：不确定时，一次用一种。 我大约 1% 的情况才用复方，而且只在已经知道自己在治什么的时候。

2. 一好转就停药

这是最大的一个，也是我看到的复发的主因。真菌很顽强——它们留在看起来完全正常的皮肤里，视觉上的清除远早于实际的清除。所以：看起来完全好了之后，再继续用一到两个星期。 这是皮肤科最便宜的保险。我会传讯息确认你有没有做到。

3. 只治疗看得见的那一块

边缘才是活跃的部分——扩散中的真菌感染，向外推进的边界才是它真正在工作的地方，中间往往比较平静。请整片都擦，而且要超出看得见的边缘。

其他部位也要治——真菌会移动。香港脚会传到指甲、也会传到腹股沟（常经由毛巾，或是穿内裤时先经过已感染的脚）。有腹股沟感染，我会检查你的脚，而且建议两边都治，否则清了一边又被另一边感染，没完没了。

4. 忽略「储藏库」

鞋子——有过脚部感染的话鞋子很可能还带着。不贵重就丢掉；要留就找鞋店专业处理。很多人认真擦了一个月药，每天早上又把脚放回感染源里。共用浴室（健身房、更衣室）请穿拖鞋，绝不打赤脚。毛巾和床单每周更换，不要共用毛巾——这是它在家人之间传播的方式。

5. 以为宠物无害

动物来源的真菌感染在本地相当常见，尤其是猫，特别是流浪猫。典型分布是小腿加双手——因为动物矮（接触小腿），而人会抱起来（用到手）。

动物来源的真菌感染常合并细菌感染，所以我会较早考虑加抗生素。别让宠物上床和枕头，毛会留在寝具很久，而且不只是皮肤问题，你也会吸进去。

关于餵流浪猫：我不会叫你停止。这对很多人有超越实用层面的意义，也不是我该置喙的。我请你做的是：穿长裤和包鞋、不要抱牠们、事后洗手和前臂、换掉餵食时穿的衣服。这样保住了你在做的事，也去掉大部分风险。下面那位病人不是因为餵猫受害，是因为光着小腿、穿拖鞋、还抱猫。

花了我三次看诊的病例

二十多岁女性，典型的金钱癣表现。我是她的第三位医生。KOH 显微镜阳性，诊断确认，我判断之前失败是因为用药不正确或不够久，于是外用加口服并安排复诊。

复诊时皮损性质变了——看起来更「凶」，比较不痒、不脱屑，但受到感染、出现黄色结痂。

我很困惑。再深入问病史：家里没有猫，但——这是追问才出来的——她喜欢餵家后面巷子的流浪猫，穿着短裤和拖鞋。

这解释了来源，也解释了黄色结痂：动物来源的真菌感染通常带着细菌。抗真菌药清掉真菌之后，细菌在皮肤上没有了竞争者，于是大量繁殖。 变得更「凶」不是治疗失败，而是治疗有效的后果。

于是抗真菌加抗生素，安排复诊。改善了，然后又变糟——药物完全没变。

再问病史：她偶尔还是会去餵猫。不是故意不听，只是她没有把我的建议连结到一件如此平常、如此善意的事。

好好谈过之后，暴露真正停止，皮损才受控并完全清除，留下一些炎症后色素沉着，我告诉她那会在几个月内消退。

我从这个病例学到的是关于我自己的事：我应该更早、用更多不同方式问动物接触史——「你有养宠物吗」和「你有接触任何动物吗」不是同一个问题。而且我应该每次复诊都重问，而不是假设讲过一次就传达到了。对她来说，在巷子餵一只流浪猫根本不算「接触动物」，那只是她去丢垃圾路上做的一件好事。

给你的重点：猫很可爱，也确实无害——直到你的皮肤屏障破损。而那个你觉得太小、太明显无关而不值得提的细节，往往就是解开谜团的那一个。

最后，一件不算错误的事

得到真菌感染不代表你不干净。这些微生物无处不在，有些本来就长期住在正常人的皮肤上。在终年流汗的湿热气候里，接触无可避免，感染很常见。这跟你洗得多仔细关系很小——而且过度搓洗会破坏皮肤屏障，反而让微生物更容易得逞。

单纯的真菌感染是完全可以根治的。 不像湿疹要长期控制，也不像黄褐斑要长期维持。是真的可以清除——只要把疗程做完、并处理感染来源。通常一星期左右会改善，两星期复诊。这一个不必失眠。

Klinik Dr Tan (Skin & Acne)，Lot 27, Ground Floor, Block D, Lintas Square, Kota Kinabalu。WhatsApp：017-234 7328。请把擦过的东西都带来。