I've never had a fire doing an herbal remedy. In Granite Falls, my main Sim family rents Lakeside Retreat, which has a better stove and grill. At home, they have the §13,000 unbreakable stove, and they have the best bar (unlocked chef bar). The cheapest stove always used to start cooking fires. The first time, the family had to wait an entire generation to get a new (cheap) stove and counter top.
If you have that new GrillZone grill (by GrillMania) from Perfect Patio Stuff, then, maybe that will help with reducing fires. I always put brick under something that can cause fires.
However, doing the Freelance Botanist aspiration will give them Naturalist as a Reward Trait, which will make them fireproof. They put out fires instantly, the blurb says.
Before that, my sim family had issues at the campfire. They kept getting burned --- especially James Polk (all of the women in my main Sim family marry former presidents) --- almost every time he went near the campfire, he would get burned. Taking a shower and/or using the soothing skin balm both take away a burn.