I think you have not fungus but contact dermatitis, that is an allergic
reactionAllergic reactions
Allergic reactions to medication
Dermatitis, reaction to tinea
Drug allergies
Febrile/cold agglutinins
Insect bite reaction - close-up
Intradermal allergy test reactions
Positive reaction to allergen
Transfusion reaction to something (toothpaste?) that came in contact with the skin. Did you put the toothpaste on your skin? If you just put it in your mouth, it wouldn't cause a rash under your arms.
In any case, if you want to get better before your holiday, you may need oral cortisone treatment. I advise you to see a doctor as soon as you can. I don't think the rash is medically serious, but it must be awfully annoying.
Also, you need to figure out what may have contacted your skin and caused the problem.
Take care.
Dr. Rockoff
The tooth mousse was only used in the mouth with no reaction inside the mouth. I have not done anything out of the ordinary in the time I got the rash and cannnot think of anything that has changed, eg washing powder or clothes.
In previous years I have had a very small rash when using a new shampoo or other that I didn't agree with, stopping use and the rash would go away in a few days. I have never had anything like this, it came up quick seemingly out of nowhere.
Thank you for your advice. I am absolutely at a loss to think what has caused it but I'll keep stretching the grey matter and see if I come up with something.
Regards, Greg.
Dr. Rockoff