。
Love and a cough cannot be hidden.
Literal
Romantic-love [and-と] cough [and-と] [topic-は] cannot-be-hidden.
A classical proverb with a vivid image: both love and coughing betray you to observers no matter how hard you try to suppress them. Note the particle structure 恋とせきとは — the second と is optional ('and so on,' closing an and-list) and は marks the whole coordinated phrase as topic. せき ('cough,' 咳 in kanji) is written in kana here. 隠せない is the potential negative of 隠す ('to hide').