Yes, diatomaceous earth can be used as a repellent for rats. Diatomaceous earth is a natural, non-toxic substance made from the fossilized remains of diatoms, which are tiny aquatic organisms. It is available in a fine powder form.

Diatomaceous earth works by dehydrating and damaging the exoskeleton of insects and pests, including rats. When rats come into contact with diatomaceous earth, the powder adheres to their bodies and absorbs the oils and fats from their exoskeleton, leading to dehydration and eventually causing their demise.

To use diatomaceous earth as a rat repellent, follow these steps:

1. Identify areas where rats are active or likely to enter, such as entry points, nesting areas, or places where you have seen rat droppings.

2. Apply a thin layer of diatomaceous earth powder in these areas, paying attention to corners, cracks, crevices, and other hiding spots.

3. Reapply the powder after rain or if it gets wet, as moisture reduces its effectiveness.

4. Monitor the affected areas for rat activity and reapply as necessary.

It's important to note that diatomaceous earth should be used with caution around pets and humans. While it is generally considered safe, it can cause respiratory irritation if inhaled in large quantities. Therefore, it's recommended to wear a mask and gloves when applying diatomaceous earth and keep it out of reach of children and pets.

Additionally, diatomaceous earth is more effective as a preventive measure or as part of an integrated pest management approach. It may not completely eliminate an existing rat infestation on its own. It's advisable to combine diatomaceous earth with other rat control methods, such as sealing entry points, removing food sources, and setting traps, for more comprehensive and effective rat management. If you have a persistent rat problem, it's best to consult with a professional pest control service for assistance.