Is it permissible to use cosmetic products to lengthen and thicken eyelashes, which return to their natural state after discontinuing their use, knowing that the suitor may think they are natural? And is that considered deception?

There is no objection to using products that lengthen and thicken eyelashes if no harm is feared from them, and this is not considered changing the creation of Allah. However, it is not permissible if it is for an improper purpose, such as deceiving a suitor, for the Messenger of Allah, may Allah bless him and grant him peace, said: "Whoever deceives us is not of us."