How To Whiten Wool How Can I Safely Whiten A Garment Hand Knitted In Raw Wool?

How can I safely whiten a garment hand knitted in raw wool? - how to whiten wool

I knit a sweater in natural / undyed, 70% wool, 30% mohair. I hope that was just a little white. Does anyone have any suggestions? One trick she learned from her grandmother, perhaps?