Deep condition with eggs. Mayonnaise is mostly eggs, so it only makes sense that eggs would also be an effective way of putting moisture and shine back in your hair. Crack 2-4 eggs into a bowl. Separate the yolk from the whites, placing the egg whites aside. A good egg white omelet might be a good way to use them up.
Pour olive oil in the bowl, just enough to cover the yolk, and whisk together. Make sure the solution is well blended.
Shampoo your hair in lukewarm water then put mixture in your hair. Let it sit for 5-6 minutes, then rinse it with cold water. Warm or hot water can scramble the egg.