Now Playing: FDA warns against 'young blood' treatments

Now Playing: This day in history: Feb. 21, 1986

Now Playing: Hangover helper? Not really, study finds

Now Playing: What is a rape kit?

Now Playing: Toothpicks injure thousands per year

Now Playing: How antibiotics mess with your gut

Now Playing: How much toothpaste is too much for kids?

Now Playing: What are PFAS?

Now Playing: How the bacteria in your gut affect your mind and body

Now Playing: Why dark chocolate is better for your health

Now Playing: Judge blocks Trump birth control coverage rules in 13 states

Now Playing: 'Tree man' suffers from rare skin condition

Now Playing: Baby hears sister's voice for first time and can't stop laughing

Now Playing: What is testicular cancer?

Now Playing: Washington state officials declare state of emergency after measles outbreak

Now Playing: Officials urge vaccinations as measles cases rise in Northwest

Now Playing: Why you should be wearing sunglasses in the winter

Now Playing: Basketball fans in Oregon unfazed by recent measles outbreak

Now Playing: What is Ewing sarcoma?

Now Playing: Tips to avoid 'cabin fever'