To treat stretch marks effectively using a Dr. Pen microneedling device, you generally need a needle depth between 1.5 mm and 3.0 mm.
Because stretch marks (striae) are actually tears that occur deep within the dermal layer of the skin—and because body skin is significantly thicker than facial skin—shallow needles simply cannot reach the depth required to break up the scar tissue and trigger new collagen production.
A more detailed breakdown helps determine the exact depth needed for specific situations:
By the Type and Age of the Stretch Marks
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New, Red/Purple Stretch Marks (Striae Rubrae): 1.5 mm and 2.0 mm.
These are still in an active, inflamed healing phase. Because they are newer, they respond faster and do not require maximum depth immediately. It is highly recommended to start at $1.5\text{mm}$ for your first few sessions to gauge your skin's tolerance.
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Old, White/Silver Stretch Marks (Striae Albae): 2.0 mm and 3.0 mm.
Older stretch marks are essentially mature, faded scar tissue. They require deeper dermal remodeling to force the skin to restart its collagen synthesis and fill in the deep "craters" or ridges.
By Body Area (Skin Thickness)
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Thinner Skin Areas (Inner Arms, Breasts, Inner Thighs): 1.5 mm
The skin on the breasts and inner arms is delicate. Going too deep here can cause tracking, severe bruising, or skin damage.
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Thicker Skin Areas (Stomach, Outer Thighs, Hips, Buttocks): 2.0 mm and 3.0 mm.
The dermis on the abdomen and glutes is quite thick and can safely tolerate deeper settings to reach the root of the stretch marks.
Important Considerations:
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Use a Numbing Cream: Depths of 1.5 mm and above on the body can be painful without a topical numbing agent (like 4% or 5% Lidocaine).
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Use the Right Cartridge: 12-pin or 16-pin cartridges are best for deep scar tissue and stretch marks because fewer needles encounter less skin resistance, allowing them to puncture cleanly to the correct depth. (Alternatively, a 36-pin can be used for broad, superficial coverage on large areas like the stomach, but it may not penetrate as deeply due to the "bed of nails" effect).
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Do NOT Drag the Pen: When working at depths of 1.5 mm to 3.0 mm, use a "stamp and lift" motion. Sliding or gliding the pen across the skin at these deep settings will slice the skin and cause micro-tears or tracking marks.
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Space Out Sessions: Deep microneedling requires a minimum of 4 to 6 weeks between sessions to allow the deep dermis to actually rebuild itself.
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Sanitization: Sterilization must be flawless to prevent deep tissue infections. Never reuse cartridges.
For official guidelines, please refer to the Dr. Pen In-Depth Guide to Microneedling or consult the FAQ section on the Dr. Pen Official website for detailed recommendations regarding treatment needles and post-procedure care.
