What can happen if my dog might have eaten a tampon?

I'm not sure if this is the cause of the problem, but my dachshund is throwing up this greenish, foamy, sticky kind of throw up. He has like 4 or 3 times and I'm pretty sure that's all he's eaten that's inside his stomach. I was wondering if he got a hold of a used tampon or pad, if it's a possibility he has toxic shock. Or could it be something that has to do with age, since he's 7 almost 8. Please help me.