Causes of Decreased Appetite (Anorexia)

1. Malignant Neoplasms

• GI cancers (stomach, pancreas, colorectal, liver)
• Lung cancer
• Lymphoma and leukemia
• Renal cell carcinoma

2. Chronic Inflammatory and Infectious Diseases

• Infections: Tuberculosis, HIV/AIDS, subacute bacterial endocarditis, fungal diseases, parasitic infections, hepatitis
• Inflammatory disorders: Rheumatoid arthritis, systemic lupus erythematosus, inflammatory bowel disease (Crohn's, ulcerative colitis)
• Organ failure: Chronic kidney disease (uremia directly suppresses appetite; leptin, TNF-alpha, and IL-6 are elevated in dialysis patients), chronic liver disease (cirrhosis), chronic heart failure, COPD

3. Metabolic and Endocrine Disorders

• Hyperthyroidism - paradoxically increases appetite in some but can cause anorexia in elderly ("apathetic thyrotoxicosis")
• Hypothyroidism
• Adrenal insufficiency (Addison's disease)
• Diabetes mellitus (especially poorly controlled or late-stage)
• Hypercalcemia (any cause)
• Hyponatremia
• Metabolic acidosis (e.g., in CKD - directly suppresses appetite)

4. Psychiatric and Psychological Causes

• Depression - one of the most common causes; appetite loss is a core DSM criterion ("SIG: E CAPS" - A = Appetite/weight disturbance)
• Anxiety disorders and panic attacks
• Anorexia nervosa / bulimia nervosa
• Grief and bereavement
• Stress
• Schizophrenia and other psychotic disorders

5. Gastrointestinal Causes

• Gastroparesis (delayed gastric emptying - causes early satiety and nausea)
• Peptic ulcer disease / gastritis
• Intestinal obstruction
• Chronic pancreatitis (pain with eating leads to food aversion)
• Celiac disease / malabsorption
• Constipation
• Acid reflux (GERD)

6. Medications and Substances

• Chemotherapy and radiation therapy (especially to the abdomen)
• Opioids (appetite suppression via mu-receptor)
• Stimulants - amphetamines, cocaine, ADHD medications (methylphenidate, amphetamine salts)
• Antibiotics (especially metronidazole, macrolides)
• Digoxin toxicity
• SSRIs / antidepressants (early treatment phase)
• Immunotherapy
• Alcohol (poor appetite, malabsorption)
• Cannabis withdrawal (paradoxically - intoxication usually stimulates appetite)

7. Neurological Causes

• Dementia (Alzheimer's, vascular dementia)
• Parkinson's disease (dysphagia, delayed gastric emptying, depression)
• Stroke
• Brain tumors (hypothalamic involvement)
• Delirium

8. Physiological / Age-Related ("Anorexia of Aging")

• Reduced chemosensory function (smell and taste decline)
• Slowed gastric emptying
• Altered neuroendocrine regulation: increased cholecystokinin (enhanced satiety), decreased ghrelin (less hunger drive), altered leptin and neuropeptide Y
• Reduced lean body mass and physical activity lowering caloric demand
• Social isolation, poverty, immobility, institutional food monotony

9. Acute and Short-Term Causes

• Viral/bacterial infections (flu, common cold, gastroenteritis)
• Food poisoning
• Postoperative state (anesthesia effect)
• Pregnancy (especially first trimester - morning sickness and hormonal changes)
• Acute pain

Summary Table

Causes of Redness in the Private (Genital) Area

1. Infections (Most Common)

Fungal

• Vulvovaginal candidiasis (Yeast infection) - Candida albicans is the most common cause in females. Signs include vulvar erythema, edema, fissures, tenderness, and white "cottage cheese" discharge. Predisposed by antibiotics, diabetes, immunosuppression, pregnancy.
• Candidal balanitis (in males) - redness, itching, and white patches on the glans penis.
• Tinea cruris ("jock itch") - Dermatophyte fungal infection of the groin; red, ring-shaped, itchy rash.

Bacterial

• Bacterial vaginosis (BV) - caused by Gardnerella vaginalis and anaerobes; malodorous discharge, mild vulvar irritation.
• Gonorrhea (Neisseria gonorrhoeae) - urethritis, cervicitis, causing redness and discharge.
• Chlamydia (Chlamydia trachomatis) - cervicitis/urethritis with redness and discharge; often asymptomatic.
• Syphilis - primary stage: a painless chancre (ulcer with red base) on genitals; secondary stage: rash including on genitals.
• Streptococcal/staphylococcal infections - cellulitis, folliculitis, abscess.
• Erythrasma - Corynebacterium minutissimum causing reddish-brown patches in groin folds.

Viral

• Genital herpes (HSV-1/HSV-2) - painful blisters/ulcers with surrounding erythema; can mimic candidal fissures. One of the most common causes of genital ulceration and redness.
• Human papillomavirus (HPV) - genital warts (condyloma acuminata); cauliflower-like growths, sometimes with surrounding redness.
• Molluscum contagiosum - pearly papules with surrounding redness.

Parasitic

• Trichomoniasis (Trichomonas vaginalis) - profuse frothy discharge, vulvar itching and redness, "strawberry cervix."
• Pubic lice (Pediculosis pubis / "crabs") - intense itching and redness from bites.
• Scabies - Sarcoptes scabiei; intensely itchy, red burrows and papules in the genital and groin area.

2. Skin Conditions (Dermatological)

• Contact/irritant dermatitis - very common; triggered by soaps, detergents, latex condoms, lubricants, scented products, sanitary pads, douches. Causes redness, burning, itching.
• Lichen sclerosus - chronic inflammatory condition; white, thin, atrophic patches with surrounding erythema; affects the vulva or glans penis; associated with risk of squamous cell carcinoma.
• Lichen planus - erosive form causes painful vulvovaginal or penile redness, ulceration, white lace-like lesions.
• Lichen simplex chronicus (LSC) - thickened, red, itchy skin from chronic scratching.
• Psoriasis - well-demarcated red plaques; in the genital area, it often lacks the typical silvery scale.
• Eczema (Atopic dermatitis) - red, dry, itchy inflamed skin; may involve the genital region.
• Seborrheic dermatitis - red, greasy, scaly patches in skin folds.

3. Sexually Transmitted Infections (STIs) - Summary

4. Hormonal / Atrophic Causes

• Atrophic vaginitis (Genitourinary syndrome of menopause) - estrogen deficiency post-menopause causes vaginal and vulvar erythema, dryness, thinning, dyspareunia, and recurrent infections.
• Post-partum estrogen deficiency - similar thinning and redness in breastfeeding mothers.

5. Inflammatory / Autoimmune Conditions

• Behcet's disease - painful genital ulcers with erythematous margins; recurrent oral and genital ulceration.
• Crohn's disease - can cause perianal/vulvar abscesses, fistulas, and erythema as an extraintestinal manifestation.
• Erythema multiforme / Stevens-Johnson syndrome - drug or infection-triggered blistering reaction; can affect genital mucosa.
• Plasma cell balanitis (Zoon's balanitis) - chronic benign red patches on the glans penis in older uncircumcised men.

6. Mechanical / Physical Causes

• Friction and chafing - tight clothing, exercise, obesity-related skin folds.
• Shaving/hair removal - razor burn, folliculitis, ingrown hairs.
• Sexual activity - friction-related redness, especially with inadequate lubrication.
• Foreign body - especially in children.

7. Other / Serious Causes

• Fournier's gangrene - rare, life-threatening necrotizing fasciitis of the perineum; starts with redness, pain, and swelling that rapidly progresses. Medical emergency.
• Extramammary Paget's disease - rare; red, eczema-like plaques on the vulva or penis; may represent underlying malignancy.
• Vulvar/penile intraepithelial neoplasia (VIN/PIN) or early carcinoma - persistent red or white patches that do not resolve.
• Fixed drug eruption - localized red/brown patch that recurs at the same site with a specific drug (e.g., NSAIDs, tetracyclines, trimethoprim).

When to See a Doctor

• Accompanied by fever, severe pain, or rapidly spreading (rule out necrotizing infection)
• Associated with painful sores or ulcers (rule out herpes, syphilis)
• Persistent beyond 1-2 weeks without an obvious cause
• Accompanied by unusual discharge (rule out STI/vaginitis)
• In a child (requires careful evaluation)