Are those menstrual teas safe?

We just don't know. Teas are made of leaves and stems and who-knows-what sprays and toxins from the soil and water. Therefore, anyone saying they are "safe" or thinking they are ok because they are "natural" has little information on which to base safety claims. If the tea is seen as medicinal, the key ingredients might have shown an effect over many years, but the data are often anecdotal. Point: buyer beware!