How Do I Deal With Damp, Mold and Mildew in the Tropics?

Are you looking for some exterior treatment for your home or some type of interior de-humidification system, or both?

As the previous response to your request indicates, inside and outside actions are different. for indoors: Use a dehydrating agent such as calcium chloride, calcium sulfate, or calcium oxide. The calcium oxide cannot be reactivated for reuse at home. The chloride can be, but it totally dissolves in the water it takes out of the air. This solution can be heated until it dries out to a solid. The sulfate remains a solid which can be dried out, by heating, for reuse. Any of these materials has a limited amount of water it can hold. A more efficient method would be to run a cold water chiller or a refrigeration unit, cooling section only, into whatever room you want dried out. Supply a drain line back out for the condensed water. Mount this unit near the top of the room and you won't need a fan on it. Keep this room closed as much as possible.

There's no remedy for damp I'm afraid: it's the climate.

Essential oils can be used to make anti-mildew spray: tea tree is used in this formula

but there are others that would work as well (juniper oil, cedar oil). Some people include vinegar in anti-mildew spray, others use borax or baking soda. But the pH effects (too acid or alkaline for the mold to grow) may not be as persistent as the effects of essential oils.

Some common spices such as cinnamon and bay have anti-mould activity.

There's probably something in your garden that would do the trick: There's been a fair bit of research on antifungal plants from Nigeria, mostly in the medicinal context but they could work on household moulds as well. That's if you want to be creative...

Household bleach with a water rinse on the outside. Dehumidifier inside.

Keep the aircon on, put light bulb in cupboard, keep all open food of any kind in the fridge, live somewhere more pleasant (been there, got the T shirt).