Encyclopedia of Health and Medicine

H
hay fever
See ALLERGIC RHINITIS.
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healing The processes and mechanisms by
which the body repairs itself. Healing represents
complex and cascading interactions among various
of the body’s systems and mechanisms.
Among the first to respond are the COAGULATION
cascade, to stop bleeding, and the IMMUNE
RESPONSE, which mobilizes T-cell lymphocytes,
macrophages, antibodies, the COMPLEMENT CASCADE,
and the release of CYTOKINES and PROSTAGLANDINS.
Fibroblasts (cells that build collagen) converge at
the site about 48 hours after the injury occurs to
begin construction of SCAR tissue. After about six
weeks the healing process turns its focus to
remodeling the collagen tissue, restoring the tissues
at the site of the injury to relatively normal
structure and appearance. This final phase of healing
lasts six months to two years, depending on
the extent of the injury.
Disease processes influence healing as well.
Chronic conditions such as DIABETES and PERIPHERAL
VASCULAR DISEASE (PVD), themselves likely the result
of inflammatory dysfunction of some sort, damage
the fine networks of nerves and BLOOD vessels that
intertwine through the tissues, limiting the ability
of these structures to carry signals (nerves) and
transport molecules and cells vital to immune function
(blood vessels). Serious injury—whether from
disease process, trauma, or major surgery—affects
endocrine and hormonal activity throughout the
body, which influence the rate and processes of
healing. Serious injury temporarily stuns the THY-
ROID GLAND, for example, resulting in reduced production
of thyroid hormones and consequential
slowing of METABOLISM (EUTHYROID SICK SYNDROME).
Although researchers can map the physiologic
steps of healing, much of healing remains a mystery.
Researchers do not fully understand what
starts, regulates, and ends the healing process.
Many integrations across neurologic, endocrine,
and immune functions are factors in healing.
Some researchers are exploring connections
between emotions and the numerous biochemical
substances that are key to the healing process.
Researchers know, for example, that emotional
stress influences the release of numerous hormones
in the body and the release of these hormones—such
as the hormone CORTISOL, a powerful
immunosuppressant—directly affects the functions
of the IMMUNE SYSTEM. Research has shown
that pain is a stressor and affects the rate of healing.
Studies continue to explore the relationship
between the mind and healing.
See also AYURVEDA; HORMONE; INTEGRATIVE MEDI-
CINE; MIND–BODY INTERACTIONS; PATHOGEN; REIKI;
STRESS RESPONSE HORMONAL CASCADE; TRADITIONAL
CHINESE MEDICINE (TCM); WOUND CARE.
histamine A chemical that acts as an IMMUNE
RESPONSE mediator. Large, granulated leukocytes
called mast cells, which reside in the mucous
membrane lining of the respiratory and gastrointestinal
tracts, store histamine in their granules
and release it during the immune response. Mast
cells are most abundant in the nasal passages
(including the SINUSES), the TRACHEA, and the
bronchi. Histamine receptors on the surfaces of
cell membranes determine how histamine affects
the cell. ANTIHISTAMINE MEDICATIONS, the cornerstone
of treatment for type I HYPERSENSITIVITY REAC-
TION (allergic reaction), work by blocking
histamine receptors.
Though there is only one form of histamine, its
release can activate any of three types of histamine
receptors: H1, H2, and H3. CYTOKINES,