If you've ever walked into an animal shelter or looked at rescue photos online, it's sometimes hard to find the real dog underneath a mop of messy fur. Stray or abandoned pets rarely look their best when they're trying to find new homes.

That's why many shelters have volunteers who bathe and groom new arrivals, knowing that even a simple makeover can help animals get adopted.

Apollo before and after grooming Apollo was used as a breeding dog in a puppy mill where he had deteriorated into a filthy mess. After a warm bath, a cute Yorkie emerged. (Photo: Wahl)

As part of its Dirty Dogs campaign, Wahl and GreaterGood.org donate funds and grooming supplies to rescues and shelters in an effort to transform more than 20,000 dogs each year to boost their chances of finding a family.

"Most dogs enter shelters wearing the effects of their harsh lives, making it difficult for adoptive families to see the lovable animal underneath the matted fur and dirt," says Steven Yde, division vice president for Wahl. "And while rescue organizations work tirelessly, the sad truth is that less than half of these dogs are getting the grooming they need due to a lack of resources."

Dorothy before and after grooming When Dorothy was found on a deserted dirt road, she was so matted her ears almost touched the ground, and her hind legs were stuck together, making it difficult to walk. But look at her after the bath and trim! (Photo: Wahl)

Since 2012, donations of Wahl’s pet shampoo have helped rescues and shelters around the United States transform more than 100,000 dogs to get them ready for adoption. You can check out hundreds of these makeovers on the Dirty Dogs Before & After Photo Gallery, read their stories and search for available dogs in your area.

To raise awareness of the importance of these makeovers, 10 of the most dramatic makeovers are part of the seventh annual Dirty Dogs Contest, and you can vote for your favorite through Aug. 21. The shelters and rescues affiliated with the top three winners will receive monetary grants: First place gets $5,000, second place earns $2,000 and third place receives $1,000.

Gabriel before and after grooming When rescuers found him, it was clear Gabriel had been severely neglected. His rescuers believe his grooming may have been the first human touch he had ever felt. (Photo: Wahl)

"A first impression at the shelter is incredibly important for adoptions. Dirty, unkempt dogs will often get overlooked by potential adopters. The goal of the Dirty Dogs Before & After Gallery is to inspire people to volunteer their time grooming and bathing animals at their local shelter, or to donate much needed money and supplies," explains Noah Horton, director of marketing and development at GreaterGood.org. "It's amazing the impact grooming can have on a dog's appearance, health and overall quality of life. And for a shelter dog, it can mean the difference between sitting in the shelter and finding a forever home."

Pepper before and after grooming Found in an abandoned home, Pepper was in desperate need of medical attention and grooming. (Photo: Wahl)

Mary Jo DiLonardo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.