Sudden bulging of left temple vein that doesn't go away - Is it treatable? (Photo)

First it needs to be clear from an examination if this is an artery or a vein. You need an in person examination to confirm this is a vein, you are concerned with.  If it is a vein, which is likely by its position treatment can be done to remove it.

A temple vein can be safely treated by sclerotherapy ( injection of a sclerosant solution, actually foam). 
A phlebectomy seems possible too. 
A temple artery would be pulsating, a simple touch will tell you the difference. 
See a vascular physician in your area if it is a vein.

Thank you for the question! It is rather difficult to fully assess your situation without an in-person exam. Such an exam would be necessary to ensure that your bulging vein is not an artery. If you do have a varicose vein, however, it can be effectively treated with sclerotherapy. This method uses a sclerosing solution that causes the vein to shrink. Usually sclerotherapy takes only 1 to 3 sessions to achieve fading of the undesirable veins.  
An in-person exam with a board-certified plastic surgeon is the best way to assess your needs and obtain expert medical advice. Best of luck!

The first thing to do is to determine if it is an artery or vein.  Ruling out temporal arteritis was important.  If it is an artery there is no treatment.  If it is vein it can be treated by either microphlebectomy or sclerotherapy.

I agree that this is very likely a prominent temple vein.  It is not common to be able to see the temporal artery through the surface of the skin (such as in your picture) and it is almost always a vein that you are seeing at that location. In rare instances you may be able to see a pulsatile temporal artery in this location in a very thin individual that has "temporal wasting".  If it has persisted this long, it is not likely to resolve without a procedure to remove it. The most common way of getting rid of unsightly temporal veins involves a temporal plastic surgery referred to as micro-phlebectomy.   It should not be a medical concerns, but rather just a cosmetic issue.

It is not clear from a picture if this is an artery or a vein. You need an in person examination.Dr H Karamanoukian#RealSelf100 Member