Thank you for the additional information and sorry for the late reply as i was offline.
ANyway coming to your query,from what you are describing it sounds like that you have a recurring bacterial infection in between the toes, now usually these infections shouldnt recur but can do so in patients who are immunocompromised or have been on steroids or have an underlying autoimmune conditions. Since you have hypothyroidism, it is possible that there is another underlying autoimmune condition which may be triggering these infections. The first step would be to get a ESR and ANA done which can be followed by a complete autoimmune profile if needed.
Secondly, another good option would be to biopsy the rash which will give an exact diagnosis of what it is, whenever you develop this rash contact your dermatologist who can biopsy it and at the same time culture the pus present in it. It will give us an idea as to which organism infect the toes and what antibiotics would work the best against it. A fungal infection must also be ruled out which would need a different sort of anti fungal to be treated. Now considering the blistery nature and location of the rash, it is possible that this is a tinea infection but not the common variety which is found. Rather this can be tinea interdigitale which classically infects the spaces between the toes can form a vesicular or blistery rash. This rash can then get secondarily infected and cause pus formation. If this is the case then skin scrapings and microscopy from the site would diagnose the problem and then you can treat it with anti fungal agents.
It is also possible that this infection is due to another type of fungus like candida etc, the skin scrapings would pick up on that as well. So basically what needs to be done here is to investigate for autoimmune possibilities, at the same time culture the area and the pus, perform skin scrapings and microscopy and if needed perform a biopsy of the rash. Im sure once these investigations are done, a cause for this can be determined.
Do you have any more questions?
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