Re: is it possible for freckles to appear later in life from medication,

Dear Lynn,

Ephelides is the common name for freckles.  They are small (<0.5 cm) 
pigmented macules (flat lesions) the may occur on sun-exposed areas.  They 
darken with UV exposure and may fade completley during the winter.  They 
usually peak in numbers during adolescence but usually occur between ages 
3 and 5.  If the lesion is really a "freckle," then it is caused by 
exposure to UV light.  "Freckles" cannot develop without sun exposure!

Risk factors for ephelides include
-blonde/red hair
-blue eyes
-skin types I, II, III
-**UV light exposure**

They are usually benign and typically disappear in older people.  They 
require no treatment although cosmetic improvements may include chemical 
peels, hydroquinones (topical bleaching creams), lasers, and topical 
retinoids (Retin-A).
Prevention includes sun avoidance and sun protection.

The differential diagnosis for freckles though is rather large.  A freckle-
looking lesion could be solar lentigo, malignant melanoma, melanocytic 
nevi, and others.

You may be referring to a solar lentigo known commonly as a sunspot, sun 
freckle, or liver spot.  They differ from ephelides in the they do NOT 
darken after sun exposure and do NOT fade in the winter.  They appear 
mostly on sun-exposed areas such as the face and back of the hands.  I 
think you might be referring to these in your question because solar 
lentigos appear usually in adulthood, usually older than age 40 and 
persist for life.

In terms of the rest of your question, medication interactions and hormone 
imbalances may cause a huge variety of problems.  This is not a usual 
cause of freckles though.  Hypoparathyroidism presents often as hot, 
flushed skin and not as freckles.

If you notice new or unusual spots on your skin, you should consult a 
physician.

Resource: medical school dermatology course.

Bonnie