Please I will apprciate your contribution on this any side effect of topping my engine every two days due to oil leakages from the oil seal damage since I have not seen a competent hands to handle it for me. Avalon 99 model

No serious effect if you are very careful and very observant with it by not allowing oil to be empty in your engine.

Damage oil seal is not a big issue. Please fix it ASAP.

depending on where the leak is coming from if its from the seal near the timing belt area belt could snap or skip causing costly damage to engine, the leak if coming from a worn out seal could deteriorate at a moments notice and cause costly damage to the engine there's no such thing as "if you are careful and observant when it comes to engine oil leaks" find the source and get it fixed or park the car.

If you plan on rebuilding the engine soon then I wouldn't worry about it and just continue to top it off.

But if it's a relatively good engine then I would change the offending seal as soon as possible.

I had a Mini Cooper with a severe rod knock that also had a bad rear main seal that was leaking. Since I planned on rebuilding the engine I ran it that way for almost 2 years.

Good luck.

I think the typical possible effects are environmental pollution, assuming the oil is entering your combustion chamber somehow, significant loss of engine power and decline in fuel economy.