Yes. Yes & yes. Nothing is safe.

Oral sex without protection (condoms or dental dams) is "safer" than vaginal or anal sex, but it is not entirely safe. Unprotected oral contact carries a risk of transmitting sexually transmitted infections (STIs) in both directions. Look for sores in and around the mouth. 👄  

Nothing is 💯 safe. Covered is best if you're stressed. Don't do anything that makes you uncomfortable.

if her customer is a male.  Infections on a male penis are generally discoverable by visual inspection.  Likewise with a provider infection that is visible on the labia.  However, an internal infection in the provider's vaginal canal is often undetectable until it has progressed to the point that it becomes painful for her, or is producing a discharge like the ones visible on males.  

the messy truth of blowjob safety is this: the sloppier, wetter, and more drool-soaked the encounter, the less the risk. Wrt your sexual health, a deluge of spit is your best friend.  

hear me out.

first, the physics of friction. dry skin rubbing on tissue is bad news because it creates microscopic tears. those tears are basically red carpets for bacteria to enter your system. a truly sloppy, spit-heavy blowjob turns your dick into a slip-and-slide. when you have a constant tsunami of drool, there is zero friction to cause those micro-tears. you want things drenched. dry == dangerous.

plus, a torrent of spit acts like a miniature carwash. pathogens need to sit still and latch onto your cells to infect you. when your partner is gurgling a ton of sloppy fluid, that river of spit flushes away bacteria and viruses before they can get anywhere near your urethra. you are essentially drowning the bad guys in real-time.

also: spit is not just water. spit is packed with mild antibacterial enzymes and antibodies evolved to neutralize invaders. a dry mouth is a stagnant breeding ground.  a mouth that is producing or overproducing spit is constantly deploying a wave of organic chemical defenses. the more fluid, the more diluted and uselss any bugs become.

this is why catching hivv from a blowjob is practically unheard of. the virus cannot survive a bath in salivary enzymes.  

even for stubborn bacterial stis like chlamydia or gonorrhea, their chances of survival plummet when they are diluted by a massive volume of sloppy fluids. they get washed away long before they can do any harm.

so, to toot my own horn, if you want to keep things safe, look for a provider who is not afraid to get sloppy. a dry, polite encounter might seem neat, but it actually carries way more risk. wrt safety, a glorious, dripping deluge of spit and fluids is your ultimate protective shield.

at the very least, it's hot.