On Monday morning, Lina noticed a small red spot on her arm. She didn’t worry. “Maybe a mosquito,” she thought. But on Tuesday, more red spots appeared on her neck and shoulders. The itching became stronger, and Lina could not stop scratching. At night, she turned in her bed again and again, unable to sleep.

On Wednesday, she went to the doctor. He looked at her skin, listened to her, and said kindly, “It is probably an allergy. But we don’t know the cause yet. The best thing is to observe your daily life. Watch what you eat, what you touch, and what you use at home. Write everything down. Sometimes the answer comes slowly.”

Lina hoped for a quick solution, but she agreed. “Okay. I will try.”

That evening, she started her “Allergy Diary.” She wrote:

Day 1: I ate pasta, salad, and apples. No change. Day 2: I cleaned the kitchen and used gloves. Still itchy. Day 3: I didn’t use perfume or lotion. No difference. Day 4: I changed my pillowcase. Still itching.

Every day she changed something, but nothing helped. The mystery continued. Lina felt frustrated. “I am a terrible detective,” she said to herself.

On Saturday morning, she decided to do laundry. She reached for the bottle of laundry detergent on the shelf. It was almost empty. Lina smiled: it was a gift from her grandmother three weeks ago — a special lavender-scented detergent from a small village shop.

She opened the bottle and smelled it. The scent was very strong, almost too strong. Suddenly, something clicked in her mind.

She remembered: The itching started after washing clothes last weekend… with this detergent.

Her heart beat faster — like a detective who finally sees the truth.

To test her idea, Lina followed a plan:

Test Day 1: She stopped using the lavender detergent. Itching became weaker. Test Day 2: She washed all her clothes and bed sheets again with her old detergent. Itching almost disappeared. Test Day 3: She wore only clothes washed with the old detergent. Itching: gone.

She looked at the lavender bottle and laughed. “So, you are the criminal!” she said.

On Sunday, Lina wrote her final case report:

Case Name: The Allergy Mystery Suspect: Lavender laundry detergent Result: Guilty Detective: Lina

She threw the bottle in the trash and said proudly, “Mystery solved. Case closed.”