No Flies On Me

There's another gold-en-re-triev-er in the village and the two dogs play well together when they meet on the morning walk. Jean-Claude and Adrienne,who take turns in this sometimes onerous duty are friendly and we have exchanged a couple of meals and looked after each others dogs from time to time.
In the long dry season we intrepid dog walkers are much plagued by little tiny flies that seem to go for the moisture in the eyes and this season Jean-Claude has taken to plucking a large fern like leaf of bracken and using it as a fan.
I have read somewhere that the pollen or spores of bracken is one of the most carcinogenic naturally occurring substances known. I have no idea what part of the plant produces this deadly substance nor at what time of the year but wondered if I ought to warn him of the danger he might be facing. In the end I decided not to- because I quite fancy his wife.
In matters of the heart (or in this case a bit lower down) it is necessary to plan ahead !!