Re: Subcutaneous testosterone injections I kind of figured it was the oil. It's just weird how I didn't even feel a knot until the third day after injection. You would think the oil would have knotted up directly after injection. And I agree that the hormone gets absorbed. But what causes the red, rashy-like area? I mean the redness for me was pretty pronounced....it was a large area. Could it be the body's way of fighting off a foreign substance (oil)?