The acids onions contain have a fading effect similar to those in lemons. These acids combined with the natural properties in apple cider vinegar help fade age spots. heres how ; finely chop an union, use a cheese cloth or strainer to extract the juice. mix one part onion juice with one part apple cider vinegar. use a cotton ball to apply the mixture to age spots, wash after 30 minutes. repeat once a day for 6 weeks and watch age spots fade away.