If you choose to collaborate with bloggers, it's important to understand the legalities of online advertising. In the UK, look at the regulations put in place by the Advertising Standards Authority, which lays down rules for advertisers, agencies and media owners.
The ASA states that if a blogger or social media influencer is given anything (payment, product, etc.) in return for coverage, then a disclaimer must be used so their audience are aware. We strongly recommend you take the time to fully understand the requirements.
In other countries there are different regulatory bodies and different regulations. Be sure to do your research to avoid issues down the line.