Fungi and yeasts build their outer wall — the cell membrane — from a fatty substance called ergosterol. Clotrimazole blocks the enzyme they need to make it. Without enough ergosterol the membrane leaks, and the fungus cannot grow or divide properly.
All the azole antifungals work this way, and it is why clotrimazole covers such a wide range: the dermatophytes behind ringworm, jock itch and athlete's foot, and Candida, the yeast that grows in warm, damp folds. Mostly it stops fungus growing rather than killing it outright. That is the practical difference from terbinafine, and it is why courses run longer. Your own skin still has to shed the infected layer, and that takes weeks whichever cream you use.
Steroid creams on the same patch, unless a doctor has told you to. Hydrocortisone takes the itch away but lets the fungus spread, and a fungal rash treated with steroid alone changes shape until it is hard to recognise.
Tight dressings or plastic over the treated area, unless advised. They push more drug into the skin and raise the chance of irritation.
Getting it in your eyes. Rinse with water if you do.
Putting clean, treated feet back into untreated shoes. Use an antifungal powder or spray in your shoes while you treat the skin, or you walk straight back into it.
Latex condoms and diaphragms in the 72 hours after using the vaginal cream or pessary. The oily base weakens latex and it can fail. This does not apply to the skin cream.
There are no meaningful interactions with medicines you swallow. Almost none of the skin cream is absorbed into the body, so alcohol, sun exposure and your other prescriptions are not an issue.
The first week
Itch and burning ease first, often within two or three days. This is the point at which most people wrongly decide it has worked.
Weeks one to two
Redness fades and the scaling settles. A ringworm patch on the body usually looks close to normal by now.
Weeks two to four
This is the part that actually clears the infection. Athlete's foot needs the full four weeks — the skin on the sole is thick and the fungus sits deeper in it.
If nothing has changed at two weeks
Either it is not fungus, or it needs something stronger. A rash that has not moved at all in two weeks is worth having looked at rather than treating for another month.
The marks afterwards
Where the rash was, skin can stay lighter or darker for weeks to months after the fungus has gone. This is far more noticeable on brown and Black skin. It is pigment change from the inflammation, not leftover infection, and more antifungal cream will not shift it.
If you finish the full course, most infections do not return on their own. You can pick the fungus up again, though, and feet are the usual route — athlete's foot comes back for a lot of people because the shoes were never treated.
If you stop early, it usually returns within a few weeks in the same place, and people then decide the cream failed. It did not. The course did.
Skin folds behave differently. Intertrigo comes back whenever the fold is warm and damp again, however well the yeast was treated. Keeping the fold dry is what prevents it; the cream only handles the flare.
There is no rebound and nothing to taper. You can stop the day the course ends.