Cyclical Blistering on One foot only

My son is 4 and for around 10 months now has endured blistering on the sole of his left foot (only) on a predictable monthly cycle. Each cycle includes around 14 days of blistering, then around 14 days where the skin heals very well. During blistering, if left unpopped a blister can grow to an inch and fills with clear liquid. We now tend to pop each blister to provide relief, but it will still leak liquid causing us to rebandage twice daily. Upto 5 main blisters will appear in each cycle. Previous diagnosis include pompholyx, but why only one foot and so cyclical? Also Herpes Simplex, but our treatment of Aciclovir appears to have no effect. We've also tried excluding some foods and cleaning products to no avail. Will try more, but again why only one foot?

[Bhupinder Kaur, MD]

Hello,
I cannot confirm a diagnosis without examination, but it can be foot blisters or fibromas.

When a foot is hot and sweaty, the sock sticks to the foot. The sock and foot then rub against each other and the inside of the shoe causing blisters to appear. Plantar fibromas are firm, nodular masses which occur as a single mass or in clusters on the arches of the foot.

Make him wear shoes that fit properly and keep feet as dry as possible. Wearing wet shoes, boots and socks will increase your chance of developing blisters. So change socks regularly.
And use foot powder to help keep your feet dry. If the blisters still persist then please get it evaluated from a dermatologist/podiatrist. The fluid from the blisters can be sent for examination.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.

[Risty]

First and foremost, thank you very much for posting your thoughts - I really appreciate you taking the time.
I note your comments on foot blisters or fibromas and will intergrate your suggestions on any future attempts to isolate the cause.
To keep you up to date, I have made a further appointment with a local consultant dermatologist. That appointment is next week when I expect the cycle of blisters to come round once more - and it is that strict cycle (monthly) along with the fact it only effects one foot that puzzle me most with all potential diagnosis.
Numerous swab tests on the fluid have revealed nothing so far. I posted a picture against my profile of the foot in question which I hope you can see.
I'll post a further update here next week after the appointment.
Thanks again.

[Bhupinder Kaur, MD]

Hello,
Even possibility like impetigo can cause blisters but they are concentrated mainly on the face, arms and legs in young children. I suggest you to get a culture sensitivity of the fluid from the blisters done from a dermatologist as it will rule out any bacterial cause of infection.

I hope it helps. Take care and regards.

[Risty]

Just to keep this post updated, I have been communicating with one other member on Med help who appears to have a similar situation with her son. I've cut/past my most recent correspondence in case there are others out there interested:

Start:
Sorry that your son's blistering has returned. The picture does look quite similar to the occurrences of my son's blistering when it's left to grow. Please do share your progress however insignificant you think it is - I'll do the same and maybe any commonality may provide clues to the root cause.
Here's a few comments and updates from me:
- I notice the blister in your photo is quite large. Over recent cycles, we have tended to pop the blister early. That clearly relies on you son being comfortable with you using a needle on it and at that age, it's a big ask. My son is used to it now - in fact he asks us to pop them because it does seem to make it a little more comfortable for him.
We bandage it for a few reasons. One to protect from infection once popped. Second to soak up the clear liquid that comes out... and there can be a lot over the course of a day or night. Third to help cushion and hopefully improve comfort.
The result of popping the blister seems to be that you get further small ones appear. So it doesn't necessarily give a net gain - just seems to allow some comfort.
- We've been using our ointment (Elocon Mometasone Furoate 0.1%) recently. This does appear to prevent a blister from developing when you catch them early. We apply it as soon as we see a pimple appear and it stops its development. However, where as previously we were in a predictable 26 day cycle (13 day blisters, 13 clean) the ointment is blurring that and instead we're almost chasing small blisters around the sole of his foot over a more prolonged period.
It's like the ointment is just postponing the blistering from developing to the size it needs to.... or that it's postponing the leaking of that clear liquid.
It will be really interesting to see how this develops. Best case, the blisters end up with nowhere to go and we suppress/control it. Worst case, we have to stop chasing the blisters (you can't use the ointment for too many consecutive days) and they develop fully as per previous cycles, before finally giving us our usual 13 day rest bite.
We've been chasing it around his foot for about 2 weeks now - so no significant blisters have been allowed to develop. I will keep you posted over the next weeks or so on how this progresses.
- We continue to take medicine to suppress Herpes Simplex. This is at the recommendation of our Consultant but we've tried and failed to cultivate Herpes Simplex from two swabs taken on two separate occasions, so there are doubts around this diagnosis. Equally, the medicine does not seem to be having any effect. Never the less, in the absence of a reasonable alternative diagnosis, it seems sensible to continue with the medicine.
- Following our last consultation at the hospital, focus seemed to return to the possibility of this being some kind of reaction i.e. an allergy. Problem is, there is no rationale for the impact only appearing on one foot - so this is the big mystery. There is nothing that I can think of that he does with one foot (left) but not the other!
End:

All further comments welcome.