Halloween tricks usually start before the holiday, and your car may be the target.

Every October, goblins, ghouls, and pranksters prowl the night and “trick” car owners by hitting their vehicles with eggs, Silly String, or smashed pumpkins. If these items are left on car paint too long, that nasty mess can cause permanent stains that not only are ugly but also can lower your vehicle’s resale value.

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Egg whites, pumpkin guts, bird droppings, bug splatter, and other substances contain acids that can eat into your car’s finish, says Jim Policare, body-shop director at Vinart Collision Center in Allentown, Pa.

If you drive a newer car, you might not have to worry. In the past 10 years, automakers have developed clearcoat paint specifically designed to resist that type of acid, says Donald White, global technology manager at DuPont Performance Coatings.

If you drive an older car, however, there are steps you can take to protect it from Halloween pranks.

Policare and White offered these tips: 

  • Wax on. Your best defense against such an attack is a protective coat of wax. The week before Halloween is a good time to apply it. It prepares your vehicle for the Halloween threats and can help protect paint from the assault of salt, sand, and road grime that comes along with winter driving in some parts of the country. For the best protection, have the wax applied by a professional detailer. Consumer Reports has tested car waxes, and the results show that most begin to wear off after only a few weeks. So we recommend waxing even new cars every two or three months, or about once a season.
  • Take cover. If you can, park the car in your garage on Halloween night or use a car cover—available at any car-parts store or online. It’s worth spending a little more to get a car cover that’s lined with a soft material so that it doesn’t scratch your paint. You’ll want one that can breathe so that moisture doesn’t build up. These covers come in a variety of sizes, and some are shaped specifically for SUVs, pickup trucks, and other vehicles.  
  • Quick rinse. If your car is hit on Halloween night, rinse off any solid residue that can scratch the paint, such as eggshells, as soon as possible. (The heat of the sun speeds up chemical reactions.) Then give your vehicle a thorough washing to get rid of any remaining material. If you do it yourself, follow our experts’ car-washing tips.
  • Be prepared to clean off any small mess quickly. Policare suggests keeping a small spray bottle of water mixed with a dedicated car-washing soap handy. A spray-on car wax will also work well. Then, whenever you find a contaminant on your car's paint—whether it’s the morning after Halloween or a bird dropping—you can spray the solution on the car, and wipe away the mess with a soft towel. Even if you can’t remove it right away, just spraying the solution on the mess will dilute the acid and minimize the damage.
  • Last resort. If a contaminant has had time to set in and cause paint damage but hasn’t eaten completely through the clearcoat layer, wash the area thoroughly and try using a cleaning wax—a product formulated with abrasives that can remove a thin layer of paint to expose the undamaged paint beneath. (Our archived car-wax ratings show which waxes offer the best cleaning and gloss improvement when we last tested.) If the damage extends through the clearcoat and into the color paint or metal, that area will probably need to be repainted.