A campaign for an Arizona teen with cancer has brought in 500,000 pictures of dogs from across the globe and several smiles. Anthony Lyons, Phoenix lymphoblastic leukemia patient, has three dogs, but he is unable to see them while undergoing chemotherapy treatments.

The 16-year-old checks into Phoenix Children’s Hospital once a month to receive his treatment. Lyons said that he sits solemnly awaiting the moment he can leave. And the only thing that lightens his mood is a visit from hospital therapy dogs. Lyons said that when the dogs arrive, they put a smile on his face. “They come in and they are already happy. They just want to see you,” Lyons said.

However, the dogs do not always come during his treatment. In an effort to keep a smile on Lyons’ face, a family friend started a Facebook page called “Photo Doggies for Anthony.” This allows him to look at dog photos anytime he chooses.

On Monday, more than 900,000 users were invited to the guest list on the event page. Roberta Lucero-Koron, creator of the Facebook event page, she could not stop crying “tears of happiness” when she discovered that the page had gone viral. She encouraged others to view the dog photos to put a smile on their faces by looking at “these beautiful animals that God gave us.”

Users as far away as Dubai and Australia posted photos of their dogs with their names and where they are from on the page. The posts began as different types of dogs, such as corgis, Chihuahuas, pooleys and huskies, but it has expanded to all types of pets. Some also offered their support by posting personal messages to Anthony.

A social media expert at Arizona State University, Retha Hill, offered an explanation for the page’s success: human emotion. Cute animals, a sick teenager and a desire to help were combined to create a successful viral sensation, according to Hill. She said that people will get involved if “they think they can make a difference.” She added that people know what they are doing has an immediate impact. “We can’t cure children’s diseases overnight but we can make this boy smile,” Hill said.

Lyons’ mother showed her gratitude for the massive support Lyons has received. She said that every photo made her and her son smile.

Currently, the Facebook event page states that it is not the “actual” event. It states that “the original photo doggies for Anthony got taken down because one person decided to bring his negativity upon a great thing.”

The current page is hosted Anthony Lyons. “I hope I can continue to see all the pictures of your dogs. No matter what they make me happy and I try and look at every single one of them,” Anthony wrote on the page. The page no longer contains 900,000 invites. However, it still has 26,000.

Anthony Lyons was diagnosed with acute lymphoblastic leukemia in July 2014. Doctors told him that his form of leukemia was treatable with time and care. Lyons will have to go in for treatments once a month for the next three years. During that time, he plans to finish high school.