As the weather warms up-- in fields, along sidewalks and wherever lawns aren't watered or mowed grass goes to seed which turn into foxtails. These are very sharp arrow like menaces nature designed to travel in one direction by endowing them with microscopic barbs just like fish hooks.
In Southern California they are a threat to your pets. They embed between toes, get into Fido's ears, up Kitteh's nose, and up Fluffy's vagina. We've removed them from eyes, noses, feet (most commonly) and even found them migrating throughout the body causing infections and abscesses.
So watch out. If Fido develops a draining tract between the toes, suddenly starts shaking his head violently or has attacks of sneezing, foxtails might be the cause. We usually have to anesthetize foxtail victims to find them and retrieve them, and sometimes looking for them can be as challenging as searching for a needle in a haystack.
I will never forget an unlucky-lucky hunting retriever we saw at UC Davis when I was a student. He suffered from lobar pneumonia for years, responded to antibiotics but the infection kept coming back. We anesthetized him and an hour long journey through his branching airways (bronchi) finally yielded a foxtail which had been lodged in his lung for ages. We were very lucky to have finally found it.
Get to know what foxtails look like and avoid them! It will save Fido and Kitteh a lot of pain and you a lot of money and grief.