Question: We recently treated a patient for a skin rash that seemed to be an allergic reaction to some unknown cause. Which diagnosis code should we use? Answer: There are several possibilities for coding the unknown skin rash. More information from the physician will help to identify the best choice. When deciding the most appropriate code, consider these options:
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You may consider selections from category 692.x (Contact dermatitis and other eczema). This category includes "Dermatitis: Not Otherwise Specified (NOS), contact, occupational, venenata"; and "Eczema (acute or chronic): NOS, allergic, erythematous, occupational."
You must also use a fourth or fifth digit with this category, which excludes certain types of dermatitis.
You may also consider these codes: allergy NOS (995.3), contact dermatitis of eyelids (373.32), dermatitis due to substances taken internally (693.0-693.9), eczema of external ear (380.22), perioral dermatitis (695.3), or urticarial reactions (708.0-708.9, 995.1).