Yes. Assuming you eat the right kind and avoid mayonnaise that's high in sugar or other carbs, then you have nothing to worry about. Since ketosis is about restricting carbs to low levels and initiating your body's consumption of fats over sugars, mayo's high-fat, low-sugar profile fits right in.
Is mayonnaise allowed on a low carb diet? Absolutely! In fact, mayonnaise is the top condiment on Keto and low carb diets. And, because it has almost no carbs and is high in fat, it makes an excellent choice for many keto recipes.
The fat in mayonnaise is perfect for the keto diet. Just be careful how much you eat since it is packed with calories. It should also be noted that mayonnaise is packed with omega-3 and omega-6 fatty acids. This is part of the unsaturated fat in mayo.
Low-carb diets work by tricking your body into assuming a physiological state that naturally burns fat at an increased speed. The body can easily withdraw from this fragile state if you eat too many carbs. Although diet sodas can be friendly to a typical low-carb diet plan, they aren't necessarily your best choice for good health.