This clinical intrapatient randomized trial will be conducted on 20 patients of both genders complaining from bilateral symmetrical striae rubra. They will be recruited from Outpatient Clinic of Dermatology Department of Cairo University Hospitals. All included patients will be subjected to:

1. Informed written consent will be taken from every patient including the study.

2. Detailed history including onset, course, duration of the disease and occupation, predisposing factors, associated diseases and previous treatments.

3. Outcome will be done at baseline, after the last session and 2 months after the last session:

   • Photographing documentation: two photographs (in appropriate views) will be taken on two occasions; before each session (Baseline), and 2 months after the last treatment session.
   • Modified Vancouver Scar Scale The modified Vancouver Scar Scale (mVSS 1) evaluates four indicators: vascularity, pigmentation, pliability and height It has a score ranging from 0-13 The modified Vancouver Scar Scale (mVSS 2) evaluates three indicators: vascularity, pliability and height It has a score ranging from 0-10
   • Dermaspectrometer Dermaspectrometer will be measure erythema index at baseline, after the last session and 2 months after the last session.
   • Histopathological Assessment Skin biopsies using 4 mm punch biopsies will be obtained from SR before treatment (baseline) and 2 months after the last treatment sessions. The post-treatment biopsy will be taken from the vicinity of the baseline biopsy. Tissues will be fixed in 10% buffered formalin, will be embedded in paraffin and will be sectioned into 5 µm-thick sections. Specimens will be stained with hematoxylin and eosin (H & E) and/or Orcein (for demonstration of elastic fibers). Histological evaluations will be carried out under a light microscopy.

Pathologic assessment for the stria will be evaluated each of the epidermis, dermis, collagen fibers and elastic fibers. Degree of improvement will be assessed by examining the following criteria.

A.Epidermis: Epidermal thickness and presence of rete ridges B.Dermis: Papillary dermal edema, dermal vascularity, and presence of skin appendages.

C.Collagen fibers will be assessed for its thickness, commenting on whether it's fibrillar, fine thickness, normal thickness or sclerotic, besides the presence of perpendicular blood vessels towards the epidermis.

D.Elastic fibers: will be evaluated it through Orcein stain for its presence or absence, its thickness if present; fragmented or fibrillar.

* Blinded investigator evaluation

Two independent blinded investigators will be assessed clinical improvement. Assessment of the standardized photographs using the following score:

-1 = worse, 0 = no change,

1. = weak (1-24% improvement in striae),

2. = moderate (25-49% improvement in striae),

3. = good (50-74%improvement in striae)

4. = excellent (75-100% improvement in striae)

   • Patients' satisfaction

The patients' self-satisfaction for each modality of treatment (regarded improvement and side effects of each modality) measured on a five-point scale:

0 → not satisfied,

1. → moderately satisfied,
2. → satisfied, Treatment Protocol Twenty patients will be subjected to Pulsed Dye Laser (PDL) on one randomized side of their bodies and carboxytherapy on the other side for four sessions with four weeks' interval between sessions. Randomization will be done through picking red (PDL) yellow (carboxytherapy) cards.

After taking photographs, patients will be locally anesthetized by topical lidocaine under occlusion for 1 h on the side of carboxytherapy. The cream will be wiped off with a wet gauze when the session started. Protective eye wear will be provided to the patient, treating doctor and all the personnel assisting the procedure.

One randomized side of the affected area will be assigned to PDL (Cynosure - Chelmsford, MA-USA) with wavelength 585 nm at a fluence 2.5-5 J/cm2, pulse duration of 0.5 ms and spot size 7 -10 mm according to the width of the striae.

The other side will be assigned to carboxytherapy (Carbo - Programmable automatic carbon dioxide therapy apparatus, MA-USA) that will be automatically calibrated to adjust the flow rate, through regulation of infusion pressure and the dosage of CO2 in ml. the infusion velocity consequently will be adjusted to a flow rate of 1 cc/sec. The injection will be performed slowly, subcutaneously, by tilting the needle at 15 degree using a sterile disposable insulin needle, with the depth adjusted at 2 mm. the gas volume per injection spot is 2ml with 1.5 cm spacing between each injection point.

Each patient will be received 4 sessions with 4 weeks' intervals.

Inclusion Criteria:

• 1. Both genders are included. 2. Patients above 18 years old. 3. Patients have bilateral symmetrical striae rubra lesions.

Exclusion Criteria:

1. Pregnancy
2. Scarring and keloid tendencies.
3. Active skin infection, active infection of herpes simplex virus.
4. Patient on Prior steroid therapy
5. Patient have History of Cushing syndrome
6. Patients with concomitant disease during the study (e.g., hepatic, renal, cardiac, autoimmune diseases, diabetes mellitus, and/or bleeding disorders).

results and discussion can be shared

after finishing the paper and and will be always available

through the pubmed