"I have no sympathy for violators of NFL drug test," reads a tweet from Dahl's verified Twitter account. "It's easy to know what goes in your body. If this was another sport what would happen?"
Irvin will miss a Week 2 game against Dahl's 49ers.
"I want to apologize to my teammates, coaches and Seahawks fans for making a mistake when I took a substance that is prohibited in the NFL without a medical exemption," Irvin said in a statement released by the team. "I am extremely disappointed in the poor judgment I showed and take full responsibility for my actions. I will not appeal the discipline and instead will focus my energy on preparing for the season so I can begin earning your trust and respect again. I look forward to contributing to the team the moment I return."