Wound Healing, Oral And Topical
Activity Of Aloe Vera
By Robert H. Davis, Ph.D.; Mark G. Leitner, R.Ph., D.P.M.; Joseph M. Russo, D.P.M. & Megan E. Byrne,
B.S.
Journal Of The American Podiatric Medical Assoc. Vol 79, Number 11, Nov 1989, P559-62
AbstractThe influence of Aloe vera, orally and topically, on wound healing was
studied. Wounds were induced on both sides of the vertebral column of ICR mice using a biopsy punch. For the oral
study, experimental animals received Aloe vera in their drinking water for 2 months, whereas the control animals
received only water. In the topical study, experimental animals were given 25% Aloe vera in Eucerin® cream
topically. The control animals received cream only. A 62.5% reduction in wound diameter was noted in mice receiving
100 mg/kg/day oral Aloe vera and a 50.80% reduction was recorded in animals receiving topical 25% Aloe vera. These
data suggest that Aloe vera is effective by both oral and topical routes of administration.
Previous studies have amply demonstrated the wound-healing influence of Aloe vera.1,
2 Aloe vera given subcutaneously showed a dose-response relationship on improvement of wound healing.
Decolorized Aloe vera (without anthraquinones) was more effective than colorized Aloe. Addition of vitamin C and
RNA did not increase the wound-healing potency of Aloe vera. Aloe vera is a natural substance containing enzymes,
amino acids, and other active ingredients that contain important properties needed for wound healing.3,
4 Aloe’s watery composition may increase the migration of epithelial cells so that an improvement of wound
healing is recorded.5-7
Rowe8 found that 50% of rats treated with Aloe vera exhibited improved wound
healing. Crewe9 reported that Aloe vera advanced healing with tissue regeneration. This response could
be explained by the fact that Aloe dilated capillaries to increase blood flow to injured areas.10 In
fact, decolorized Aloe vera improved wound healing in a dose-related fashion even in the diabetic
animals,11 in which the healing of vascular tissue was impaired. Possibly, there are specific factors
that Aloe vera overcomes to improve wound healing. In normal and diabetic animals, Aloe vera possesses
anti-inflammatory, antiedemic, and improved healing properties. This study attempts to show the oral and topical
activity of Aloe vera in improving wound healing.
Materials And MethodsIn the oral study, adult male ICR mice (35 to 45 gm, 8
animals/group) received food grade Aloe vera for 2 months in their drinking water. The control animals did not
receive any Aloe vera. The mice were anesthetized and shaved on both sides of the back. A 6-mm punch biopsy was
used to induce two skin wounds on each side of the vertebral column. The diameters of the wounds were measured from
anterior to posterior with a Vernier® caliper. Standard errors and p-values were subsequently calculated.
For the topical study, the materials and methods were as follows: adult male ICR mice (35
to 45 gm, 10 animals/group) were anesthetized and shaved on both sides of the back, and two wounds were made on
either side of the vertebral columns of each animal. The wounds were induced by a 6-mm punch biopsy.
Anterior-to-posterior measurements of the wounds were recorded by a Vernier caliper on days 1, 4, and 7. One group
of experimental mice received 25% colorized Aloe vera topically on each wound daily for 6 days. The total
application was 200 mg. A second experimental control group received topical Eucerin cream alone. Untreated mice
served as a non-treatment control. The standard errors were calculated, and the p-values were
obtained.12
Results And DiscussionNormal wound healing occurs in three stages: inflammation,
proliferation, and remodeling. The wound healing process depends on a given provision of local circulation, as well
as the formation and deposition of collagen. A considerable amount of evidence has shown that Aloe vera improves
wound and burn healing in animals and humans.13 Some studies found that 50% of rats showed improved
wound healing over 7 days.8, 9 Aloe given subcutaneously showed a dose-response relationship on
improvement of wounds. A similar response was recorded in diabetics, whose wounds normally are characterized by
poor or delayed healing.11
Current methods used to treat difficult wounds include debridement, irrigation,
antibiotics, tissue grafts, proteolytic enzymes, and corticosteroids, which possess major drawbacks and unwanted
side effects. Aloe vera contains important ingredients necessary for wound healing, such as vitamin C (ascorbic
acid), amino acids, vitamin E, and zinc.13, 14 Ascorbic acid enhances the synthesis of collagen and
counterbalances collagen breakdown.15, 16 Vitamin E is a fat-soluble vitamin found in Aloe that has
proven anti-oxidant activity. It may help stabilize lysosomal enzymes needed to synthesize collagen and it prevents
free radical damage (cross-linkage) that appears to be detrimental to normal wound healing.13, 17 It was
demonstrated in the authors’ laboratory that zinc improved the tensile strength of wounds, thus improving
healing.18 Aloe vera penetrates, cleanses, and dilates capillaries going to an injured site, which also
improves healing. Aloe vera may hasten epithelialization of wounds and reduce dehydration necrosis.
Several factors delay or reduce wound healing, including bacterial infections, necrotic
tissue, interference with blood supply, lymphatic blockage, and diabetes mellitus. These conditions that inhibit
wound healing can be combined under the classification, of “tissue anoxia,”19 or reduction of oxygen in
body tissue below physiologic levels. If tissue anoxia could be altered by regional superoxygenation, an increased
healing rate could be achieved.
It was found in the authors’ laboratory that Aloe vera was effective orally in promoting
wound healing. Oral food-grade Aloe vera (100 mg/kg/day) improved wound healing compared to the healing of control
animals receiving only water (Table 1, Figure 1). The decrease in wound diameters for the control animals
was 3.5 +/- 0.3 mm (51.1%), whereas the Aloe-treated mice had a decrease in wound diameters by as much as 4.8 +/-
0.5 mm (62.5%). The difference was significant at p <0.05.
Table 1
Effect of oral Aloe vera on wound healing in mice over a 2-month
period. |
Table 1
Effect of oral Aloe vera on wound healing in mice over a 2-month
period. |
|
Decrease in Wound Diameter
|
|
MM
|
% Decrease
|
| Control |
3.5 +/- 0.3
|
51.1 +/- 4.2
|
| Aloe |
4.8 +/- 0.5*
|
62.5 +/- 5.4
|
| 100 mg/kg/day |
|
|
| 8 Animals/Group; *p <0.05 |
|
Figure 1
Effect of oral Aloe vera on wound healing in mice over a
2-month period. |
Moreover, the laboratory found that Aloe vera administered topically
also served to improve wound healing. Table 2 and Figure 2 depict the effect of topical, 25%
colorized Aloe vera in mice over a period of 7 days. The wounds on the mice that received 25 %
colorized Aloe vera demonstrated a 3.9 +/- 0.4-mm reduction in diameter, as compared to the
wound diameter reduction of 1.9 +/- 0.3 mm (p <0.001) for the animals that received cream
alone. No significant difference was observed between the untreated wounds and the wounds
treated with Eucerin cream alone (p >0.5). Therefore, the percentages of decrease in wound
diameters for the nontreatment control group, cream alone control group, and cream plus 25%
Aloe vera group were 32.5% +/- 4.8%, 25.4% +/- 3.4%, and 50.8% +/- 3.6%, respectively. These
findings clearly suggest that 25% colorized Aloe vera was a significant factor in the healing
of the wounds. Since oxygen is required for the synthesis of collagen by
fibroblasts,20 Aloe vera may improve the vascular supply and make more oxygen
available to improve collagen formation for wound healing.
Table 2
Topical effect of Aloe vera on wound healing in mice over a 7-day
period. |
|
Decrease in Wound Diameter
|
|
MM
|
% Decrease
|
| Control |
2.1 +/- 0.4
|
32.5 +/- 4.8
|
| Cream Alone |
1.9 +/- 0.3
|
25.4 +/- 3.4
|
| +25% Aloe |
3.9 +/- 0.4
|
50.8 +/- 3.6
|
| 10 Animals/Group; *p <0.001 |
 |
Figure 2
Topical effect of Aloe vera on wound healing in mice over a
7-day period. |
It also was observed that the animals not receiving topical Aloe had
hard and crusty wounds, which generally appeared unclean. However, the Aloe-treated wounds were
clean, with healthy granulation tissue. The presence of Aloe seemed to reduce the amount of
dead tissue at the wound site and provide better wound healing. Previous studies by the authors
have shown that the wounds of mice receiving 100 mg/kg of colorized Aloe vera had better
vascularity and healthier looking granulation tissue. Mice receiving decolorized Aloe vera had
an even firmer connective tissue and the appearance of more vascularization.
During the wound-healing process, epithelial cells proliferate,
migrate from the edges of the wound, and eventually cover the wound with skin. By lysing
collagen with enzymes, the epithelial cells move across the wound and attach to viable tissue.
The proliferation and migration of the epithelial cells are dependent on an adequate supply of
oxygen. Therefore, the increased presence of oxygen, caused by the Aloe vera improving
microcirculation, should greatly improve the wound-healing process.21 It is
hypothesized that catecholamines (epinephrine and norepinephrine) retard epithelial cell
proliferation.22 When a wound is sustained, the supply of catecholamines is
interrupted, and the barrier to mitosis is removed. Thus, cells begin to grow and divide.
Possibly, some constituents of Aloe vera may either block catecholamines or directly stimulate
epithelialization to improve wound healing.
During early wound healing, the vascular and lymphatic systems are of
primary importance. Failure or delay of vascular regeneration decreases oxygen transport to the
wound, which subsequently depresses the mobilization of excessive fluids from the wound site.
The wound becomes edematous, leading to further damage, infection, and eventually cell death.
In wound healing, new blood vessels sprout up from platelets or macrophages to keep the wound
open-ended. Hypoxia may be a stimulant to revascularization. Aloe may, thus, achieve the
following effects to improve tissue healing: an increased blood supply, and, hence, an
increased oxygen supply to the wound by blocking vasoconstrictive compounds (inflammation
stage); greater migration of epidermal cells over moist tissue caused by factors and enzymes
present in Aloe vera (proliferation stage); and extensive reorientation of collagen fibers
caused by a stronger cross-linking (remodeling stage).23 Aloe vera also provides for
a clean wound free of excess exudate and contamination, making it a favorable treatment for
wounds.
The authors’ histologic work indicates that Aloe vera stimulates and
enhances vascularity around the wound area. As a result, the general appearance of the wound
is, in all respects, healthier than the untreated control wound. It may be that Aloe vera
increases the supply of oxygen to the wound. This is further evidence to support the theory
that an increase in oxygen availability improves wound healing. Furthermore, Aloe vera can
topically reduce inflammation and depress the symptoms of adjuvant arthritis.
SummaryThe authors’ studies have shown that Aloe vera improves
wound healing when administered either orally or topically. It not only contributes to a
decrease in wound diameter, but also leads to better vascularity and healthier granulation
tissue. The fact that Aloe is effective orally suggests that it is not broken down by the
gastrointestinal tract and is absorbed into the blood. Aloe possibly improves wound healing by
increasing the availability of oxygen and by increasing the synthesis and the strength of
Collagen. Aloe vera has become a subject of scientific study concerning inflammation and wound
healing. As knowledge about Aloe increases, significant benefits of a practical nature in the
management of healing wounds can be expected.
References
|
Whole Leaf Aloe Vera - Wound Healing, Oral And Topical Activity Of Aloe Vera
|