It might be mold. This is what I thought when I found streaks like this in my mucous when I was getting a sinus and ear infection about three weeks ago. So I have been treating it like a fungal infection.
I have been taking a tablespoon of Apple Cider Vinegar in water three times a day and it seems to be drying up my sinuses. I also put one drop of cayenne extract under my tongue several times a day. This helps alleviate that allergic feeling. I have also been doing a colon (bowel cleanse).
Now I don't see any more of those moldy-looking streaks in my mucous.